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Existence and Uniqueness Linear Independence Matrices and Determinants Linear Independence Revisited Solution Theorem Theory of Linear Ordinary Differential Equations Bernd Schr oder logo1 Bernd Schr oder Louisiana Tech University,


  1. Existence and Uniqueness Linear Independence Matrices and Determinants Linear Independence Revisited Solution Theorem Proof of the Superposition Principle a n ( x ) y ( n ) 1 ( x )+ ··· + a 1 ( x ) y ′ 1 ( x )+ a 0 ( x ) y 1 ( x ) = 0 a n ( x ) y ( n ) 2 ( x )+ ··· + a 1 ( x ) y ′ 2 ( x )+ a 0 ( x ) y 2 ( x ) = 0 a n ( x ) y ( n ) � � 1 ( x ) + ··· + a 0 ( x ) y 1 ( x ) = c 1 · 0 c 1 a n ( x ) y ( n ) � � + c 2 2 ( x ) + ··· + a 0 ( x ) y 2 ( x ) = c 2 · 0 logo1 Bernd Schr¨ oder Louisiana Tech University, College of Engineering and Science Theory of Linear Ordinary Differential Equations

  2. Existence and Uniqueness Linear Independence Matrices and Determinants Linear Independence Revisited Solution Theorem Proof of the Superposition Principle a n ( x ) y ( n ) 1 ( x )+ ··· + a 1 ( x ) y ′ 1 ( x )+ a 0 ( x ) y 1 ( x ) = 0 a n ( x ) y ( n ) 2 ( x )+ ··· + a 1 ( x ) y ′ 2 ( x )+ a 0 ( x ) y 2 ( x ) = 0 a n ( x ) y ( n ) � � 1 ( x ) + ··· + a 0 ( x ) y 1 ( x ) = c 1 · 0 c 1 a n ( x ) y ( n ) � � + c 2 2 ( x ) + ··· + a 0 ( x ) y 2 ( x ) = c 2 · 0 a n ( x )( c 1 y 1 ) ( n ) ( x ) + ··· + a 0 ( x )( c 1 y 1 )( x ) = 0 logo1 Bernd Schr¨ oder Louisiana Tech University, College of Engineering and Science Theory of Linear Ordinary Differential Equations

  3. Existence and Uniqueness Linear Independence Matrices and Determinants Linear Independence Revisited Solution Theorem Proof of the Superposition Principle a n ( x ) y ( n ) 1 ( x )+ ··· + a 1 ( x ) y ′ 1 ( x )+ a 0 ( x ) y 1 ( x ) = 0 a n ( x ) y ( n ) 2 ( x )+ ··· + a 1 ( x ) y ′ 2 ( x )+ a 0 ( x ) y 2 ( x ) = 0 a n ( x ) y ( n ) � � 1 ( x ) + ··· + a 0 ( x ) y 1 ( x ) = c 1 · 0 c 1 a n ( x ) y ( n ) � � + c 2 2 ( x ) + ··· + a 0 ( x ) y 2 ( x ) = c 2 · 0 a n ( x )( c 1 y 1 ) ( n ) ( x ) + ··· + a 0 ( x )( c 1 y 1 )( x ) = 0 a n ( x )( c 2 y 2 ) ( n ) ( x ) � � + + ··· + a 0 ( x )( c 2 y 2 )( x ) = 0 logo1 Bernd Schr¨ oder Louisiana Tech University, College of Engineering and Science Theory of Linear Ordinary Differential Equations

  4. Existence and Uniqueness Linear Independence Matrices and Determinants Linear Independence Revisited Solution Theorem Proof of the Superposition Principle a n ( x ) y ( n ) 1 ( x )+ ··· + a 1 ( x ) y ′ 1 ( x )+ a 0 ( x ) y 1 ( x ) = 0 a n ( x ) y ( n ) 2 ( x )+ ··· + a 1 ( x ) y ′ 2 ( x )+ a 0 ( x ) y 2 ( x ) = 0 a n ( x ) y ( n ) � � 1 ( x ) + ··· + a 0 ( x ) y 1 ( x ) = c 1 · 0 c 1 a n ( x ) y ( n ) � � + c 2 2 ( x ) + ··· + a 0 ( x ) y 2 ( x ) = c 2 · 0 a n ( x )( c 1 y 1 ) ( n ) ( x ) + ··· + a 0 ( x )( c 1 y 1 )( x ) = 0 a n ( x )( c 2 y 2 ) ( n ) ( x ) � � + + ··· + a 0 ( x )( c 2 y 2 )( x ) = 0 a n ( x )( c 1 y 1 + c 2 y 2 ) ( n ) ( x ) + ··· + a 0 ( x )( c 1 y 1 + c 2 y 2 )( x ) = 0 logo1 Bernd Schr¨ oder Louisiana Tech University, College of Engineering and Science Theory of Linear Ordinary Differential Equations

  5. Existence and Uniqueness Linear Independence Matrices and Determinants Linear Independence Revisited Solution Theorem Handling Inhomogeneous Equations logo1 Bernd Schr¨ oder Louisiana Tech University, College of Engineering and Science Theory of Linear Ordinary Differential Equations

  6. Existence and Uniqueness Linear Independence Matrices and Determinants Linear Independence Revisited Solution Theorem Handling Inhomogeneous Equations For the linear inhomogeneous differential equation a n ( x ) y ( n ) ( x )+ a n − 1 ( x ) y ( n − 1 ) ( x )+ ··· + a 1 ( x ) y ′ ( x )+ a 0 ( x ) y ( x ) = g ( x ) let y h ( x ) denote the general solution of the corresponding homogeneous equation. Moreover let y p ( x ) be one particular solution of the inhomogeneous equation. Then the general solution of the inhomogeneous equation is y ( x ) = y p ( x )+ y h ( x ) . logo1 Bernd Schr¨ oder Louisiana Tech University, College of Engineering and Science Theory of Linear Ordinary Differential Equations

  7. Existence and Uniqueness Linear Independence Matrices and Determinants Linear Independence Revisited Solution Theorem Handling Inhomogeneous Equations For the linear inhomogeneous differential equation a n ( x ) y ( n ) ( x )+ a n − 1 ( x ) y ( n − 1 ) ( x )+ ··· + a 1 ( x ) y ′ ( x )+ a 0 ( x ) y ( x ) = g ( x ) let y h ( x ) denote the general solution of the corresponding homogeneous equation. Moreover let y p ( x ) be one particular solution of the inhomogeneous equation. Then the general solution of the inhomogeneous equation is y ( x ) = y p ( x )+ y h ( x ) . So the theory of inhomogeneous equations is pretty much reduced to that of homogeneous equations. logo1 Bernd Schr¨ oder Louisiana Tech University, College of Engineering and Science Theory of Linear Ordinary Differential Equations

  8. Existence and Uniqueness Linear Independence Matrices and Determinants Linear Independence Revisited Solution Theorem Proof logo1 Bernd Schr¨ oder Louisiana Tech University, College of Engineering and Science Theory of Linear Ordinary Differential Equations

  9. Existence and Uniqueness Linear Independence Matrices and Determinants Linear Independence Revisited Solution Theorem Proof a n ( x ) y ( n ) p ( x ) + ··· + a 0 ( x ) y p ( x ) = g ( x ) logo1 Bernd Schr¨ oder Louisiana Tech University, College of Engineering and Science Theory of Linear Ordinary Differential Equations

  10. Existence and Uniqueness Linear Independence Matrices and Determinants Linear Independence Revisited Solution Theorem Proof a n ( x ) y ( n ) p ( x ) + ··· + a 0 ( x ) y p ( x ) = g ( x ) a n ( x ) y ( n ) � � + h ( x ) + ··· + a 0 ( x ) y h ( x ) = 0 logo1 Bernd Schr¨ oder Louisiana Tech University, College of Engineering and Science Theory of Linear Ordinary Differential Equations

  11. Existence and Uniqueness Linear Independence Matrices and Determinants Linear Independence Revisited Solution Theorem Proof a n ( x ) y ( n ) p ( x ) + ··· + a 0 ( x ) y p ( x ) = g ( x ) a n ( x ) y ( n ) � � + h ( x ) + ··· + a 0 ( x ) y h ( x ) = 0 a n ( x )( y p + y h ) ( n ) ( x ) + ··· + a 0 ( x )( y p + y h )( x ) = g ( x ) logo1 Bernd Schr¨ oder Louisiana Tech University, College of Engineering and Science Theory of Linear Ordinary Differential Equations

  12. Existence and Uniqueness Linear Independence Matrices and Determinants Linear Independence Revisited Solution Theorem Proof a n ( x ) y ( n ) p ( x ) + ··· + a 0 ( x ) y p ( x ) = g ( x ) a n ( x ) y ( n ) � � + h ( x ) + ··· + a 0 ( x ) y h ( x ) = 0 a n ( x )( y p + y h ) ( n ) ( x ) + ··· + a 0 ( x )( y p + y h )( x ) = g ( x ) and logo1 Bernd Schr¨ oder Louisiana Tech University, College of Engineering and Science Theory of Linear Ordinary Differential Equations

  13. Existence and Uniqueness Linear Independence Matrices and Determinants Linear Independence Revisited Solution Theorem Proof a n ( x ) y ( n ) p ( x ) + ··· + a 0 ( x ) y p ( x ) = g ( x ) a n ( x ) y ( n ) � � + h ( x ) + ··· + a 0 ( x ) y h ( x ) = 0 a n ( x )( y p + y h ) ( n ) ( x ) + ··· + a 0 ( x )( y p + y h )( x ) = g ( x ) and a n ( x ) y ( n ) i ( x ) + ··· + a 0 ( x ) y i ( x ) = g ( x ) logo1 Bernd Schr¨ oder Louisiana Tech University, College of Engineering and Science Theory of Linear Ordinary Differential Equations

  14. Existence and Uniqueness Linear Independence Matrices and Determinants Linear Independence Revisited Solution Theorem Proof a n ( x ) y ( n ) p ( x ) + ··· + a 0 ( x ) y p ( x ) = g ( x ) a n ( x ) y ( n ) � � + h ( x ) + ··· + a 0 ( x ) y h ( x ) = 0 a n ( x )( y p + y h ) ( n ) ( x ) + ··· + a 0 ( x )( y p + y h )( x ) = g ( x ) and a n ( x ) y ( n ) i ( x ) + ··· + a 0 ( x ) y i ( x ) = g ( x ) a n ( x ) y ( n ) � � − p ( x ) + ··· + a 0 ( x ) y p ( x ) = g ( x ) logo1 Bernd Schr¨ oder Louisiana Tech University, College of Engineering and Science Theory of Linear Ordinary Differential Equations

  15. Existence and Uniqueness Linear Independence Matrices and Determinants Linear Independence Revisited Solution Theorem Proof a n ( x ) y ( n ) p ( x ) + ··· + a 0 ( x ) y p ( x ) = g ( x ) a n ( x ) y ( n ) � � + h ( x ) + ··· + a 0 ( x ) y h ( x ) = 0 a n ( x )( y p + y h ) ( n ) ( x ) + ··· + a 0 ( x )( y p + y h )( x ) = g ( x ) and a n ( x ) y ( n ) i ( x ) + ··· + a 0 ( x ) y i ( x ) = g ( x ) a n ( x ) y ( n ) � � − p ( x ) + ··· + a 0 ( x ) y p ( x ) = g ( x ) a n ( x )( y i − y p ) ( n ) ( x ) + ··· + a 0 ( x )( y i − y p )( x ) = 0 logo1 Bernd Schr¨ oder Louisiana Tech University, College of Engineering and Science Theory of Linear Ordinary Differential Equations

  16. Existence and Uniqueness Linear Independence Matrices and Determinants Linear Independence Revisited Solution Theorem Linear Combinations of Vectors logo1 Bernd Schr¨ oder Louisiana Tech University, College of Engineering and Science Theory of Linear Ordinary Differential Equations

  17. Existence and Uniqueness Linear Independence Matrices and Determinants Linear Independence Revisited Solution Theorem Linear Combinations of Vectors How do we actually know that several vectors “point in different directions”? logo1 Bernd Schr¨ oder Louisiana Tech University, College of Engineering and Science Theory of Linear Ordinary Differential Equations

  18. Existence and Uniqueness Linear Independence Matrices and Determinants Linear Independence Revisited Solution Theorem Linear Combinations of Vectors How do we actually know that several vectors “point in different directions”? Let � v 1 ,� v 2 ,...,� v n be vectors. Then any sum n ∑ � v i = c 1 � v 1 + c 2 � v 2 + ··· + c n � c i v n i = 1 with the c i being real numbers is called a linear combination of the vectors. logo1 Bernd Schr¨ oder Louisiana Tech University, College of Engineering and Science Theory of Linear Ordinary Differential Equations

  19. Existence and Uniqueness Linear Independence Matrices and Determinants Linear Independence Revisited Solution Theorem Linear Independence for Vectors logo1 Bernd Schr¨ oder Louisiana Tech University, College of Engineering and Science Theory of Linear Ordinary Differential Equations

  20. Existence and Uniqueness Linear Independence Matrices and Determinants Linear Independence Revisited Solution Theorem Linear Independence for Vectors A set of n vectors { v 1 , ··· ,� v n } is called linearly dependent if � and only if there are numbers c 1 ,..., c n , which are not all zero, v n = � 0 , where � � v 1 + ··· + c n � such that c 1 0 denotes the null vector , for which all components are zero. logo1 Bernd Schr¨ oder Louisiana Tech University, College of Engineering and Science Theory of Linear Ordinary Differential Equations

  21. Existence and Uniqueness Linear Independence Matrices and Determinants Linear Independence Revisited Solution Theorem Linear Independence for Vectors A set of n vectors { v 1 , ··· ,� v n } is called linearly dependent if � and only if there are numbers c 1 ,..., c n , which are not all zero, v n = � 0 , where � � v 1 + ··· + c n � such that c 1 0 denotes the null vector , for which all components are zero. If no such numbers exist, the set of vectors is called linearly independent . That is, a set of n vectors { v 1 , ··· ,� v n } is called � linearly independent if and only if the only numbers c 1 , ··· , c n , n v i = � ∑ 0 are c 1 = c 2 = ··· = c n = 0. for which c i � i = 1 logo1 Bernd Schr¨ oder Louisiana Tech University, College of Engineering and Science Theory of Linear Ordinary Differential Equations

  22. Existence and Uniqueness Linear Independence Matrices and Determinants Linear Independence Revisited Solution Theorem Determine if the vectors ( 1 , 1 , 3 ) , ( 2 , 4 , 2 ) and ( 3 , − 1 , 4 ) are linearly independent. logo1 Bernd Schr¨ oder Louisiana Tech University, College of Engineering and Science Theory of Linear Ordinary Differential Equations

  23. Existence and Uniqueness Linear Independence Matrices and Determinants Linear Independence Revisited Solution Theorem Determine if the vectors ( 1 , 1 , 3 ) , ( 2 , 4 , 2 ) and ( 3 , − 1 , 4 ) are linearly independent.         1 2 3 0  =  + c 2  + c 3 − 1 c 1 1 4 0      3 2 4 0 logo1 Bernd Schr¨ oder Louisiana Tech University, College of Engineering and Science Theory of Linear Ordinary Differential Equations

  24. Existence and Uniqueness Linear Independence Matrices and Determinants Linear Independence Revisited Solution Theorem Determine if the vectors ( 1 , 1 , 3 ) , ( 2 , 4 , 2 ) and ( 3 , − 1 , 4 ) are linearly independent.         1 2 3 0  =  + c 2  + c 3 − 1 c 1 1 4 0      3 2 4 0 + + = 1 c 1 2 c 2 3 c 3 0 logo1 Bernd Schr¨ oder Louisiana Tech University, College of Engineering and Science Theory of Linear Ordinary Differential Equations

  25. Existence and Uniqueness Linear Independence Matrices and Determinants Linear Independence Revisited Solution Theorem Determine if the vectors ( 1 , 1 , 3 ) , ( 2 , 4 , 2 ) and ( 3 , − 1 , 4 ) are linearly independent.         1 2 3 0  =  + c 2  + c 3 − 1 c 1 1 4 0      3 2 4 0 + + = 1 c 1 2 c 2 3 c 3 0 + − = 1 c 1 4 c 2 1 c 3 0 logo1 Bernd Schr¨ oder Louisiana Tech University, College of Engineering and Science Theory of Linear Ordinary Differential Equations

  26. Existence and Uniqueness Linear Independence Matrices and Determinants Linear Independence Revisited Solution Theorem Determine if the vectors ( 1 , 1 , 3 ) , ( 2 , 4 , 2 ) and ( 3 , − 1 , 4 ) are linearly independent.         1 2 3 0  =  + c 2  + c 3 − 1 c 1 1 4 0      3 2 4 0 + + = 1 c 1 2 c 2 3 c 3 0 + − = 1 c 1 4 c 2 1 c 3 0 + + = 3 c 1 2 c 2 4 c 3 0 logo1 Bernd Schr¨ oder Louisiana Tech University, College of Engineering and Science Theory of Linear Ordinary Differential Equations

  27. Existence and Uniqueness Linear Independence Matrices and Determinants Linear Independence Revisited Solution Theorem Determine if the vectors ( 1 , 1 , 3 ) , ( 2 , 4 , 2 ) and ( 3 , − 1 , 4 ) are linearly independent. logo1 Bernd Schr¨ oder Louisiana Tech University, College of Engineering and Science Theory of Linear Ordinary Differential Equations

  28. Existence and Uniqueness Linear Independence Matrices and Determinants Linear Independence Revisited Solution Theorem Determine if the vectors ( 1 , 1 , 3 ) , ( 2 , 4 , 2 ) and ( 3 , − 1 , 4 ) are linearly independent. + 2 c 2 + 3 c 3 = 0 c 1 + − = c 1 4 c 2 c 3 0 3 c 1 + 2 c 2 + 4 c 3 = 0 logo1 Bernd Schr¨ oder Louisiana Tech University, College of Engineering and Science Theory of Linear Ordinary Differential Equations

  29. Existence and Uniqueness Linear Independence Matrices and Determinants Linear Independence Revisited Solution Theorem Determine if the vectors ( 1 , 1 , 3 ) , ( 2 , 4 , 2 ) and ( 3 , − 1 , 4 ) are linearly independent. + 2 c 2 + 3 c 3 = 0 c 1 + − = c 1 4 c 2 c 3 0 3 c 1 + 2 c 2 + 4 c 3 = 0 c 1 + 2 c 2 + 3 c 3 = 0 logo1 Bernd Schr¨ oder Louisiana Tech University, College of Engineering and Science Theory of Linear Ordinary Differential Equations

  30. Existence and Uniqueness Linear Independence Matrices and Determinants Linear Independence Revisited Solution Theorem Determine if the vectors ( 1 , 1 , 3 ) , ( 2 , 4 , 2 ) and ( 3 , − 1 , 4 ) are linearly independent. + 2 c 2 + 3 c 3 = 0 c 1 + − = c 1 4 c 2 c 3 0 3 c 1 + 2 c 2 + 4 c 3 = 0 c 1 + 2 c 2 + 3 c 3 = 0 − = 2 c 2 4 c 3 0 logo1 Bernd Schr¨ oder Louisiana Tech University, College of Engineering and Science Theory of Linear Ordinary Differential Equations

  31. Existence and Uniqueness Linear Independence Matrices and Determinants Linear Independence Revisited Solution Theorem Determine if the vectors ( 1 , 1 , 3 ) , ( 2 , 4 , 2 ) and ( 3 , − 1 , 4 ) are linearly independent. + 2 c 2 + 3 c 3 = 0 c 1 + − = c 1 4 c 2 c 3 0 3 c 1 + 2 c 2 + 4 c 3 = 0 c 1 + 2 c 2 + 3 c 3 = 0 − = 2 c 2 4 c 3 0 − − = 4 c 2 5 c 3 0 logo1 Bernd Schr¨ oder Louisiana Tech University, College of Engineering and Science Theory of Linear Ordinary Differential Equations

  32. Existence and Uniqueness Linear Independence Matrices and Determinants Linear Independence Revisited Solution Theorem Determine if the vectors ( 1 , 1 , 3 ) , ( 2 , 4 , 2 ) and ( 3 , − 1 , 4 ) are linearly independent. + 2 c 2 + 3 c 3 = 0 c 1 + − = c 1 4 c 2 c 3 0 3 c 1 + 2 c 2 + 4 c 3 = 0 c 1 + 2 c 2 + 3 c 3 = 0 − = 2 c 2 4 c 3 0 − − = 4 c 2 5 c 3 0 + + = c 1 2 c 2 3 c 3 0 − = 2 c 2 4 c 3 0 logo1 Bernd Schr¨ oder Louisiana Tech University, College of Engineering and Science Theory of Linear Ordinary Differential Equations

  33. Existence and Uniqueness Linear Independence Matrices and Determinants Linear Independence Revisited Solution Theorem Determine if the vectors ( 1 , 1 , 3 ) , ( 2 , 4 , 2 ) and ( 3 , − 1 , 4 ) are linearly independent. + 2 c 2 + 3 c 3 = 0 c 1 + − = c 1 4 c 2 c 3 0 3 c 1 + 2 c 2 + 4 c 3 = 0 c 1 + 2 c 2 + 3 c 3 = 0 − = 2 c 2 4 c 3 0 − − = 4 c 2 5 c 3 0 + + = c 1 2 c 2 3 c 3 0 − = 2 c 2 4 c 3 0 − = 13 c 3 0 logo1 Bernd Schr¨ oder Louisiana Tech University, College of Engineering and Science Theory of Linear Ordinary Differential Equations

  34. Existence and Uniqueness Linear Independence Matrices and Determinants Linear Independence Revisited Solution Theorem Determine if the vectors ( 1 , 1 , 3 ) , ( 2 , 4 , 2 ) and ( 3 , − 1 , 4 ) are linearly independent. + 2 c 2 + 3 c 3 = 0 c 1 + − = c 1 4 c 2 c 3 0 3 c 1 + 2 c 2 + 4 c 3 = 0 c 1 + 2 c 2 + 3 c 3 = 0 − = 2 c 2 4 c 3 0 − − = 4 c 2 5 c 3 0 + + = c 1 2 c 2 3 c 3 0 − = 2 c 2 4 c 3 0 − = 13 c 3 0 0 = c 3 logo1 Bernd Schr¨ oder Louisiana Tech University, College of Engineering and Science Theory of Linear Ordinary Differential Equations

  35. Existence and Uniqueness Linear Independence Matrices and Determinants Linear Independence Revisited Solution Theorem Determine if the vectors ( 1 , 1 , 3 ) , ( 2 , 4 , 2 ) and ( 3 , − 1 , 4 ) are linearly independent. + 2 c 2 + 3 c 3 = 0 c 1 + − = c 1 4 c 2 c 3 0 3 c 1 + 2 c 2 + 4 c 3 = 0 c 1 + 2 c 2 + 3 c 3 = 0 − = 2 c 2 4 c 3 0 − − = 4 c 2 5 c 3 0 + + = c 1 2 c 2 3 c 3 0 − = 2 c 2 4 c 3 0 − = 13 c 3 0 0 = c 3 = c 2 logo1 Bernd Schr¨ oder Louisiana Tech University, College of Engineering and Science Theory of Linear Ordinary Differential Equations

  36. Existence and Uniqueness Linear Independence Matrices and Determinants Linear Independence Revisited Solution Theorem Determine if the vectors ( 1 , 1 , 3 ) , ( 2 , 4 , 2 ) and ( 3 , − 1 , 4 ) are linearly independent. + 2 c 2 + 3 c 3 = 0 c 1 + − = c 1 4 c 2 c 3 0 3 c 1 + 2 c 2 + 4 c 3 = 0 c 1 + 2 c 2 + 3 c 3 = 0 − = 2 c 2 4 c 3 0 − − = 4 c 2 5 c 3 0 + + = c 1 2 c 2 3 c 3 0 − = 2 c 2 4 c 3 0 − = 13 c 3 0 0 = c 3 = c 2 = c 1 logo1 Bernd Schr¨ oder Louisiana Tech University, College of Engineering and Science Theory of Linear Ordinary Differential Equations

  37. Existence and Uniqueness Linear Independence Matrices and Determinants Linear Independence Revisited Solution Theorem Determine if the vectors ( 1 , 1 , 3 ) , ( 2 , 4 , 2 ) and ( 3 , − 1 , 4 ) are linearly independent. + 2 c 2 + 3 c 3 = 0 c 1 + − = c 1 4 c 2 c 3 0 3 c 1 + 2 c 2 + 4 c 3 = 0 c 1 + 2 c 2 + 3 c 3 = 0 − = 2 c 2 4 c 3 0 − − = 4 c 2 5 c 3 0 + + = c 1 2 c 2 3 c 3 0 − = 2 c 2 4 c 3 0 − = 13 c 3 0 0 = c 3 = c 2 = c 1 , and the vectors are linearly independent. logo1 Bernd Schr¨ oder Louisiana Tech University, College of Engineering and Science Theory of Linear Ordinary Differential Equations

  38. Existence and Uniqueness Linear Independence Matrices and Determinants Linear Independence Revisited Solution Theorem       − 1 2 3  and  are − 2 − 2 Determine if  , 2    − 4 − 5 3 linearly independent. logo1 Bernd Schr¨ oder Louisiana Tech University, College of Engineering and Science Theory of Linear Ordinary Differential Equations

  39. Existence and Uniqueness Linear Independence Matrices and Determinants Linear Independence Revisited Solution Theorem       − 1 2 3  and  are − 2 − 2 Determine if  , 2    − 4 − 5 3 linearly independent. − + = 2 c 1 1 c 2 3 c 3 0 logo1 Bernd Schr¨ oder Louisiana Tech University, College of Engineering and Science Theory of Linear Ordinary Differential Equations

  40. Existence and Uniqueness Linear Independence Matrices and Determinants Linear Independence Revisited Solution Theorem       − 1 2 3  and  are − 2 − 2 Determine if  , 2    − 4 − 5 3 linearly independent. − + = 2 c 1 1 c 2 3 c 3 0 − 2 c 1 + − = 2 c 2 2 c 3 0 logo1 Bernd Schr¨ oder Louisiana Tech University, College of Engineering and Science Theory of Linear Ordinary Differential Equations

  41. Existence and Uniqueness Linear Independence Matrices and Determinants Linear Independence Revisited Solution Theorem       − 1 2 3  and  are − 2 − 2 Determine if  , 2    − 4 − 5 3 linearly independent. − + = 2 c 1 1 c 2 3 c 3 0 − 2 c 1 + − = 2 c 2 2 c 3 0 − 4 c 1 + − = 3 c 2 5 c 3 0 logo1 Bernd Schr¨ oder Louisiana Tech University, College of Engineering and Science Theory of Linear Ordinary Differential Equations

  42. Existence and Uniqueness Linear Independence Matrices and Determinants Linear Independence Revisited Solution Theorem − + = 2 c 1 c 2 3 c 3 0 − 2 c 1 + 2 c 2 − 2 c 3 = 0 − 4 c 1 + − = 3 c 2 5 c 3 0 logo1 Bernd Schr¨ oder Louisiana Tech University, College of Engineering and Science Theory of Linear Ordinary Differential Equations

  43. Existence and Uniqueness Linear Independence Matrices and Determinants Linear Independence Revisited Solution Theorem − + = 2 c 1 c 2 3 c 3 0 − 2 c 1 + 2 c 2 − 2 c 3 = 0 − 4 c 1 + − = 3 c 2 5 c 3 0 − + = 2 c 1 c 2 3 c 3 0 logo1 Bernd Schr¨ oder Louisiana Tech University, College of Engineering and Science Theory of Linear Ordinary Differential Equations

  44. Existence and Uniqueness Linear Independence Matrices and Determinants Linear Independence Revisited Solution Theorem − + = 2 c 1 c 2 3 c 3 0 − 2 c 1 + 2 c 2 − 2 c 3 = 0 − 4 c 1 + − = 3 c 2 5 c 3 0 − + = 2 c 1 c 2 3 c 3 0 c 2 + c 3 = 0 logo1 Bernd Schr¨ oder Louisiana Tech University, College of Engineering and Science Theory of Linear Ordinary Differential Equations

  45. Existence and Uniqueness Linear Independence Matrices and Determinants Linear Independence Revisited Solution Theorem − + = 2 c 1 c 2 3 c 3 0 − 2 c 1 + 2 c 2 − 2 c 3 = 0 − 4 c 1 + − = 3 c 2 5 c 3 0 − + = 2 c 1 c 2 3 c 3 0 c 2 + c 3 = 0 + = c 2 c 3 0 logo1 Bernd Schr¨ oder Louisiana Tech University, College of Engineering and Science Theory of Linear Ordinary Differential Equations

  46. Existence and Uniqueness Linear Independence Matrices and Determinants Linear Independence Revisited Solution Theorem − + = 2 c 1 c 2 3 c 3 0 − 2 c 1 + 2 c 2 − 2 c 3 = 0 − 4 c 1 + − = 3 c 2 5 c 3 0 − + = 2 c 1 c 2 3 c 3 0 c 2 + c 3 = 0 + = c 2 c 3 0 c 2 = − c 3 logo1 Bernd Schr¨ oder Louisiana Tech University, College of Engineering and Science Theory of Linear Ordinary Differential Equations

  47. Existence and Uniqueness Linear Independence Matrices and Determinants Linear Independence Revisited Solution Theorem − + = 2 c 1 c 2 3 c 3 0 − 2 c 1 + 2 c 2 − 2 c 3 = 0 − 4 c 1 + − = 3 c 2 5 c 3 0 − + = 2 c 1 c 2 3 c 3 0 c 2 + c 3 = 0 + = c 2 c 3 0 c 2 = − c 3 , c 1 = c 2 − 3 c 3 2 logo1 Bernd Schr¨ oder Louisiana Tech University, College of Engineering and Science Theory of Linear Ordinary Differential Equations

  48. Existence and Uniqueness Linear Independence Matrices and Determinants Linear Independence Revisited Solution Theorem − + = 2 c 1 c 2 3 c 3 0 − 2 c 1 + 2 c 2 − 2 c 3 = 0 − 4 c 1 + − = 3 c 2 5 c 3 0 − + = 2 c 1 c 2 3 c 3 0 c 2 + c 3 = 0 + = c 2 c 3 0 c 2 = − c 3 , c 1 = c 2 − 3 c 3 , 2 choose c 3 = 1 logo1 Bernd Schr¨ oder Louisiana Tech University, College of Engineering and Science Theory of Linear Ordinary Differential Equations

  49. Existence and Uniqueness Linear Independence Matrices and Determinants Linear Independence Revisited Solution Theorem − + = 2 c 1 c 2 3 c 3 0 − 2 c 1 + 2 c 2 − 2 c 3 = 0 − 4 c 1 + − = 3 c 2 5 c 3 0 − + = 2 c 1 c 2 3 c 3 0 c 2 + c 3 = 0 + = c 2 c 3 0 c 2 = − c 3 , c 1 = c 2 − 3 c 3 , 2 choose c 3 = 1: c 2 = − 1 logo1 Bernd Schr¨ oder Louisiana Tech University, College of Engineering and Science Theory of Linear Ordinary Differential Equations

  50. Existence and Uniqueness Linear Independence Matrices and Determinants Linear Independence Revisited Solution Theorem − + = 2 c 1 c 2 3 c 3 0 − 2 c 1 + 2 c 2 − 2 c 3 = 0 − 4 c 1 + − = 3 c 2 5 c 3 0 − + = 2 c 1 c 2 3 c 3 0 c 2 + c 3 = 0 + = c 2 c 3 0 c 2 = − c 3 , c 1 = c 2 − 3 c 3 , 2 choose c 3 = 1: c 2 = − 1, c 1 = − 2. logo1 Bernd Schr¨ oder Louisiana Tech University, College of Engineering and Science Theory of Linear Ordinary Differential Equations

  51. Existence and Uniqueness Linear Independence Matrices and Determinants Linear Independence Revisited Solution Theorem − + = 2 c 1 c 2 3 c 3 0 − 2 c 1 + 2 c 2 − 2 c 3 = 0 − 4 c 1 + − = 3 c 2 5 c 3 0 − + = 2 c 1 c 2 3 c 3 0 c 2 + c 3 = 0 + = c 2 c 3 0 c 2 = − c 3 , c 1 = c 2 − 3 c 3 , 2 choose c 3 = 1: c 2 = − 1, c 1 = − 2.         2 − 1 3 0  = − 2 − 2  −  + − 2 2 0      − 4 3 − 5 0 logo1 Bernd Schr¨ oder Louisiana Tech University, College of Engineering and Science Theory of Linear Ordinary Differential Equations

  52. Existence and Uniqueness Linear Independence Matrices and Determinants Linear Independence Revisited Solution Theorem − + = 2 c 1 c 2 3 c 3 0 − 2 c 1 + 2 c 2 − 2 c 3 = 0 − 4 c 1 + − = 3 c 2 5 c 3 0 − + = 2 c 1 c 2 3 c 3 0 c 2 + c 3 = 0 + = c 2 c 3 0 c 2 = − c 3 , c 1 = c 2 − 3 c 3 , 2 choose c 3 = 1: c 2 = − 1, c 1 = − 2.         2 − 1 3 0  =  , − 2 − 2  −  + − 2 2 0     − 4 3 − 5 0 and the vectors are linearly dependent. logo1 Bernd Schr¨ oder Louisiana Tech University, College of Engineering and Science Theory of Linear Ordinary Differential Equations

  53. Existence and Uniqueness Linear Independence Matrices and Determinants Linear Independence Revisited Solution Theorem Why use Matrices? logo1 Bernd Schr¨ oder Louisiana Tech University, College of Engineering and Science Theory of Linear Ordinary Differential Equations

  54. Existence and Uniqueness Linear Independence Matrices and Determinants Linear Independence Revisited Solution Theorem Why use Matrices? 1 1 3 logo1 Bernd Schr¨ oder Louisiana Tech University, College of Engineering and Science Theory of Linear Ordinary Differential Equations

  55. Existence and Uniqueness Linear Independence Matrices and Determinants Linear Independence Revisited Solution Theorem Why use Matrices? 1 2 1 4 3 2 logo1 Bernd Schr¨ oder Louisiana Tech University, College of Engineering and Science Theory of Linear Ordinary Differential Equations

  56. Existence and Uniqueness Linear Independence Matrices and Determinants Linear Independence Revisited Solution Theorem Why use Matrices? 1 2 3 − 1 1 4 3 2 4 logo1 Bernd Schr¨ oder Louisiana Tech University, College of Engineering and Science Theory of Linear Ordinary Differential Equations

  57. Existence and Uniqueness Linear Independence Matrices and Determinants Linear Independence Revisited Solution Theorem Why use Matrices? 1 2 3 − 1 1 4 3 2 4 logo1 Bernd Schr¨ oder Louisiana Tech University, College of Engineering and Science Theory of Linear Ordinary Differential Equations

  58. Existence and Uniqueness Linear Independence Matrices and Determinants Linear Independence Revisited Solution Theorem Matrices logo1 Bernd Schr¨ oder Louisiana Tech University, College of Engineering and Science Theory of Linear Ordinary Differential Equations

  59. Existence and Uniqueness Linear Independence Matrices and Determinants Linear Independence Revisited Solution Theorem Matrices Let m and n be positive integers. An m × n -matrix is a rectangular array of mn numbers a ij , commonly indexed and written as follows.  ···  a 11 a 12 a 1 ( n − 1 ) a 1 n ··· a 21 a 22 a 2 ( n − 1 ) a 2 n     ··· a 31 a 32 a 3 ( n − 1 ) a 3 n   A =( a i , j ) i = 1 ,..., m =   . . . .   . . j = 1 ,..., n     a ( m − 1 ) 1 a ( m − 1 ) 2 ··· a ( m − 1 )( n − 1 ) a ( m − 1 ) n   a m 1 a m 2 ··· a m ( n − 1 ) a mn The index i is called the row index and the index j is called the column index . logo1 Bernd Schr¨ oder Louisiana Tech University, College of Engineering and Science Theory of Linear Ordinary Differential Equations

  60. Existence and Uniqueness Linear Independence Matrices and Determinants Linear Independence Revisited Solution Theorem Determinants logo1 Bernd Schr¨ oder Louisiana Tech University, College of Engineering and Science Theory of Linear Ordinary Differential Equations

  61. Existence and Uniqueness Linear Independence Matrices and Determinants Linear Independence Revisited Solution Theorem Determinants � a 11 � a 12 Let A = be a 2 × 2 matrix. Then we define the a 21 a 22 determinant of A to be � �� � a 11 � � a 11 a 12 a 12 � � det ( A ) : = det : = � : = a 11 a 22 − a 12 a 21 . � � a 21 a 22 a 21 a 22 � logo1 Bernd Schr¨ oder Louisiana Tech University, College of Engineering and Science Theory of Linear Ordinary Differential Equations

  62. Existence and Uniqueness Linear Independence Matrices and Determinants Linear Independence Revisited Solution Theorem Determinants � a 11 � a 12 Let A = be a 2 × 2 matrix. Then we define the a 21 a 22 determinant of A to be � �� � a 11 � � a 11 a 12 a 12 � � det ( A ) : = det : = � : = a 11 a 22 − a 12 a 21 . � � a 21 a 22 a 21 a 22 � Let A = ( a ij ) i , j = 1 ,..., n be a square matrix and let A ij be the matrix obtained by erasing the i th row and the j th column. Then the determinant of A is defined recursively by n n ( − 1 ) i + j a ij det ( A ij ) = ( − 1 ) i + j a ij det ( A ij ) , ∑ ∑ det ( A ) : = | A | : = j = 1 i = 1 where the i in the first sum is an arbitrary row and the j in the second sum is an arbitrary column. logo1 Bernd Schr¨ oder Louisiana Tech University, College of Engineering and Science Theory of Linear Ordinary Differential Equations

  63. Existence and Uniqueness Linear Independence Matrices and Determinants Linear Independence Revisited Solution Theorem Uses of the Determinant logo1 Bernd Schr¨ oder Louisiana Tech University, College of Engineering and Science Theory of Linear Ordinary Differential Equations

  64. Existence and Uniqueness Linear Independence Matrices and Determinants Linear Independence Revisited Solution Theorem Uses of the Determinant 1. The determinant gives the n -dimensional volume of the parallelepiped spanned by the column vectors. logo1 Bernd Schr¨ oder Louisiana Tech University, College of Engineering and Science Theory of Linear Ordinary Differential Equations

  65. Existence and Uniqueness Linear Independence Matrices and Determinants Linear Independence Revisited Solution Theorem Uses of the Determinant 1. The determinant gives the n -dimensional volume of the parallelepiped spanned by the column vectors. 2. The n -dimensional vectors � v 1 ,...,� v n are linearly independent if and only if det ( � v 1 ,...,� v n ) � = 0 , where ( v n ) denotes a matrix whose columns are the � v 1 ,...,� vectors � v i . logo1 Bernd Schr¨ oder Louisiana Tech University, College of Engineering and Science Theory of Linear Ordinary Differential Equations

  66. Existence and Uniqueness Linear Independence Matrices and Determinants Linear Independence Revisited Solution Theorem Uses of the Determinant 1. The determinant gives the n -dimensional volume of the parallelepiped spanned by the column vectors. 2. The n -dimensional vectors � v 1 ,...,� v n are linearly independent if and only if det ( � v 1 ,...,� v n ) � = 0 , where ( v n ) denotes a matrix whose columns are the � v 1 ,...,� vectors � v i . 3. Computation of characteristic polynomials. logo1 Bernd Schr¨ oder Louisiana Tech University, College of Engineering and Science Theory of Linear Ordinary Differential Equations

  67. Existence and Uniqueness Linear Independence Matrices and Determinants Linear Independence Revisited Solution Theorem       1 2 3  and  are linearly − 1 Determine if 1  , 4    3 2 4 independent. logo1 Bernd Schr¨ oder Louisiana Tech University, College of Engineering and Science Theory of Linear Ordinary Differential Equations

  68. Existence and Uniqueness Linear Independence Matrices and Determinants Linear Independence Revisited Solution Theorem       1 2 3  and  are linearly − 1 Determine if 1  , 4    3 2 4 independent. 1 2 3 − 1 det 1 4 3 2 4 logo1 Bernd Schr¨ oder Louisiana Tech University, College of Engineering and Science Theory of Linear Ordinary Differential Equations

  69. Existence and Uniqueness Linear Independence Matrices and Determinants Linear Independence Revisited Solution Theorem       1 2 3  and  are linearly − 1 Determine if 1  , 4    3 2 4 independent. 1 2 3 − 1 det 1 4 3 2 4 logo1 Bernd Schr¨ oder Louisiana Tech University, College of Engineering and Science Theory of Linear Ordinary Differential Equations

  70. Existence and Uniqueness Linear Independence Matrices and Determinants Linear Independence Revisited Solution Theorem       1 2 3  and  are linearly − 1 Determine if 1  , 4    3 2 4 independent. 1 2 3 − 1 det 1 4 3 2 4 � 4 � − 1 = 1 · det 2 4 logo1 Bernd Schr¨ oder Louisiana Tech University, College of Engineering and Science Theory of Linear Ordinary Differential Equations

  71. Existence and Uniqueness Linear Independence Matrices and Determinants Linear Independence Revisited Solution Theorem       1 2 3  and  are linearly − 1 Determine if 1  , 4    3 2 4 independent. 1 2 3 − 1 det 1 4 3 2 4 � 4 � − 1 = 1 · det 2 4 logo1 Bernd Schr¨ oder Louisiana Tech University, College of Engineering and Science Theory of Linear Ordinary Differential Equations

  72. Existence and Uniqueness Linear Independence Matrices and Determinants Linear Independence Revisited Solution Theorem       1 2 3  and  are linearly − 1 Determine if 1  , 4    3 2 4 independent. 1 2 3 − 1 det 1 4 3 2 4 � 4 � − 1 = 1 · det 2 4 logo1 Bernd Schr¨ oder Louisiana Tech University, College of Engineering and Science Theory of Linear Ordinary Differential Equations

  73. Existence and Uniqueness Linear Independence Matrices and Determinants Linear Independence Revisited Solution Theorem       1 2 3  and  are linearly − 1 Determine if 1  , 4    3 2 4 independent. 1 2 3 − 1 det 1 4 3 2 4 � 4 � � 2 � − 1 3 = 1 · det − 1 · det 2 4 2 4 logo1 Bernd Schr¨ oder Louisiana Tech University, College of Engineering and Science Theory of Linear Ordinary Differential Equations

  74. Existence and Uniqueness Linear Independence Matrices and Determinants Linear Independence Revisited Solution Theorem       1 2 3  and  are linearly − 1 Determine if 1  , 4    3 2 4 independent. 1 2 3 − 1 det 1 4 3 2 4 � 4 � � 2 � − 1 3 = 1 · det − 1 · det 2 4 2 4 logo1 Bernd Schr¨ oder Louisiana Tech University, College of Engineering and Science Theory of Linear Ordinary Differential Equations

  75. Existence and Uniqueness Linear Independence Matrices and Determinants Linear Independence Revisited Solution Theorem       1 2 3  and  are linearly − 1 Determine if 1  , 4    3 2 4 independent. 1 2 3 − 1 det 1 4 3 2 4 � 4 � � 2 � − 1 3 = 1 · det − 1 · det 2 4 2 4 logo1 Bernd Schr¨ oder Louisiana Tech University, College of Engineering and Science Theory of Linear Ordinary Differential Equations

  76. Existence and Uniqueness Linear Independence Matrices and Determinants Linear Independence Revisited Solution Theorem       1 2 3  and  are linearly − 1 Determine if 1  , 4    3 2 4 independent. 1 2 3 − 1 det 1 4 3 2 4 � 4 � � 2 � � 2 � − 1 3 3 = 1 · det − 1 · det + 3 · det 2 4 2 4 4 − 1 logo1 Bernd Schr¨ oder Louisiana Tech University, College of Engineering and Science Theory of Linear Ordinary Differential Equations

  77. Existence and Uniqueness Linear Independence Matrices and Determinants Linear Independence Revisited Solution Theorem       1 2 3  and  are linearly − 1 Determine if 1  , 4    3 2 4 independent. 1 2 3 − 1 det 1 4 3 2 4 � 4 � � 2 � � 2 � − 1 3 3 = 1 · det − 1 · det + 3 · det 2 4 2 4 4 − 1 logo1 Bernd Schr¨ oder Louisiana Tech University, College of Engineering and Science Theory of Linear Ordinary Differential Equations

  78. Existence and Uniqueness Linear Independence Matrices and Determinants Linear Independence Revisited Solution Theorem       1 2 3  and  are linearly − 1 Determine if 1  , 4    3 2 4 independent. 1 2 3 − 1 det 1 4 3 2 4 � 4 � � 2 � � 2 � − 1 3 3 = 1 · det − 1 · det + 3 · det 2 4 2 4 4 − 1 = 1 · 18 logo1 Bernd Schr¨ oder Louisiana Tech University, College of Engineering and Science Theory of Linear Ordinary Differential Equations

  79. Existence and Uniqueness Linear Independence Matrices and Determinants Linear Independence Revisited Solution Theorem       1 2 3  and  are linearly − 1 Determine if 1  , 4    3 2 4 independent. 1 2 3 − 1 det 1 4 3 2 4 � 4 � � 2 � � 2 � − 1 3 3 = 1 · det − 1 · det + 3 · det 2 4 2 4 4 − 1 = 1 · 18 − 1 · 2 logo1 Bernd Schr¨ oder Louisiana Tech University, College of Engineering and Science Theory of Linear Ordinary Differential Equations

  80. Existence and Uniqueness Linear Independence Matrices and Determinants Linear Independence Revisited Solution Theorem       1 2 3  and  are linearly − 1 Determine if 1  , 4    3 2 4 independent. 1 2 3 − 1 det 1 4 3 2 4 � 4 � � 2 � � 2 � − 1 3 3 = 1 · det − 1 · det + 3 · det 2 4 2 4 4 − 1 = 1 · 18 − 1 · 2 + 3 · ( − 14 ) logo1 Bernd Schr¨ oder Louisiana Tech University, College of Engineering and Science Theory of Linear Ordinary Differential Equations

  81. Existence and Uniqueness Linear Independence Matrices and Determinants Linear Independence Revisited Solution Theorem       1 2 3  and  are linearly − 1 Determine if 1  , 4    3 2 4 independent. 1 2 3 − 1 det 1 4 3 2 4 � 4 � � 2 � � 2 � − 1 3 3 = 1 · det − 1 · det + 3 · det 2 4 2 4 4 − 1 = 1 · 18 − 1 · 2 + 3 · ( − 14 ) = − 26 logo1 Bernd Schr¨ oder Louisiana Tech University, College of Engineering and Science Theory of Linear Ordinary Differential Equations

  82. Existence and Uniqueness Linear Independence Matrices and Determinants Linear Independence Revisited Solution Theorem       1 2 3  and  are linearly − 1 Determine if 1  , 4    3 2 4 independent. 1 2 3 − 1 det 1 4 3 2 4 � 4 � � 2 � � 2 � − 1 3 3 = 1 · det − 1 · det + 3 · det 2 4 2 4 4 − 1 = 1 · 18 − 1 · 2 + 3 · ( − 14 ) = − 26 � = 0 logo1 Bernd Schr¨ oder Louisiana Tech University, College of Engineering and Science Theory of Linear Ordinary Differential Equations

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