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SECTION 8-5
              Matrices and Determinants




Tue, Apr 12
ESSENTIAL QUESTIONS

              How do you find the determinant of a 2X2 matrix?
              How do you solve systems of equations using
              determinants?


              Where you’ll see this:
                Sports, construction, fitness



Tue, Apr 12
VOCABULARY
              1. Square Matrix:


              2. Determinant:


              3. Cramer’s Rule:




Tue, Apr 12
VOCABULARY
              1. Square Matrix: A matrix with the same number of rows
               and columns

              2. Determinant:


              3. Cramer’s Rule:




Tue, Apr 12
VOCABULARY
              1. Square Matrix: A matrix with the same number of rows
               and columns
                                              ⎡a b ⎤
              2. Determinant: In a 2X2 matrix ⎢    ⎥ , det A = ad - bc.
                                              ⎣c d ⎦

              3. Cramer’s Rule:




Tue, Apr 12
VOCABULARY
              1. Square Matrix: A matrix with the same number of rows
               and columns
                                              ⎡a b ⎤
              2. Determinant: In a 2X2 matrix ⎢    ⎥ , det A = ad - bc.
                                              ⎣c d ⎦

              3. Cramer’s Rule: A method of using determinants of
               matrices to solve systems of equations




Tue, Apr 12
MATRIX
              m x n: m rows and n columns




Tue, Apr 12
MATRIX
              m x n: m rows and n columns


               ⎡ −2 2 3 ⎤           ⎡3 −1⎤
               ⎢        ⎥           ⎢    ⎥   ⎡4 −3 0 ⎤
                                             ⎣       ⎦
               ⎣ 9 6 −3 ⎦           ⎣5 8 ⎦




Tue, Apr 12
MATRIX
              m x n: m rows and n columns


               ⎡ −2 2 3 ⎤           ⎡3 −1⎤
               ⎢        ⎥           ⎢    ⎥   ⎡4 −3 0 ⎤
                                             ⎣       ⎦
               ⎣ 9 6 −3 ⎦           ⎣5 8 ⎦

                 2X3




Tue, Apr 12
MATRIX
              m x n: m rows and n columns


               ⎡ −2 2 3 ⎤           ⎡3 −1⎤
               ⎢        ⎥           ⎢    ⎥   ⎡4 −3 0 ⎤
                                             ⎣       ⎦
               ⎣ 9 6 −3 ⎦           ⎣5 8 ⎦

                 2X3               2X2




Tue, Apr 12
MATRIX
              m x n: m rows and n columns


               ⎡ −2 2 3 ⎤           ⎡3 −1⎤
               ⎢        ⎥           ⎢    ⎥   ⎡4 −3 0 ⎤
                                             ⎣       ⎦
               ⎣ 9 6 −3 ⎦           ⎣5 8 ⎦

                 2X3               2X2         1X3




Tue, Apr 12
DETERMINANT


                        a b
                det A =     = ad − bc
                        c d




Tue, Apr 12
EXAMPLE 1
                                      ⎡0 4 ⎤
              Find the determinant of ⎢    ⎥.
                                      ⎣6 7 ⎦




Tue, Apr 12
EXAMPLE 1
                                      ⎡0 4 ⎤
              Find the determinant of ⎢    ⎥.
                                      ⎣6 7 ⎦
                         ad − bc




Tue, Apr 12
EXAMPLE 1
                                      ⎡0 4 ⎤
              Find the determinant of ⎢    ⎥.
                                      ⎣6 7 ⎦
                         ad − bc
                     = 0(7) − 4(6)




Tue, Apr 12
EXAMPLE 1
                                      ⎡0 4 ⎤
              Find the determinant of ⎢    ⎥.
                                      ⎣6 7 ⎦
                         ad − bc
                     = 0(7) − 4(6)
                       = 0 − 24



Tue, Apr 12
EXAMPLE 1
                                      ⎡0 4 ⎤
              Find the determinant of ⎢    ⎥.
                                      ⎣6 7 ⎦
                         ad − bc
                     = 0(7) − 4(6)
                       = 0 − 24
                         = −24

Tue, Apr 12
CRAMER’S RULE




Tue, Apr 12
CRAMER’S RULE

              1. Make sure equations look like Ax + By = C.




Tue, Apr 12
CRAMER’S RULE

              1. Make sure equations look like Ax + By = C.
              2. Make a 2X2 determinant matrix: x in 1st column, y in
                 2nd, call A.




Tue, Apr 12
CRAMER’S RULE

              1. Make sure equations look like Ax + By = C.
              2. Make a 2X2 determinant matrix: x in 1st column, y in
                 2nd, call A.
              3. Make a new 2X2 determinant matrix: Replace x
                 column with equation answers, call Ax.




Tue, Apr 12
CRAMER’S RULE

              1. Make sure equations look like Ax + By = C.
              2. Make a 2X2 determinant matrix: x in 1st column, y in
                 2nd, call A.
              3. Make a new 2X2 determinant matrix: Replace x
                 column with equation answers, call Ax.
              4. Make another 2X2 determinant matrix: Replace y
                 column with equation answers, call Ay.


Tue, Apr 12
CRAMER’S RULE




Tue, Apr 12
CRAMER’S RULE



              5. Divide Ax by A and Ay by A.




Tue, Apr 12
CRAMER’S RULE



              5. Divide Ax by A and Ay by A.
              6. Check answer and rewrite solution.




Tue, Apr 12
EXAMPLE 2
              Solve the system of equations using Cramer’s rule (matrices).
              ⎧3x − 7 y = −6
              ⎨
              ⎩ x + 2 y = 11




Tue, Apr 12
EXAMPLE 2
              Solve the system of equations using Cramer’s rule (matrices).
              ⎧3x − 7 y = −6      3 −7
              ⎨                A=
              ⎩ x + 2 y = 11      1 2




Tue, Apr 12
EXAMPLE 2
              Solve the system of equations using Cramer’s rule (matrices).
              ⎧3x − 7 y = −6      3 −7            −6 −7
              ⎨                A=            Ax =
              ⎩ x + 2 y = 11      1 2             11 2




Tue, Apr 12
EXAMPLE 2
              Solve the system of equations using Cramer’s rule (matrices).
              ⎧3x − 7 y = −6      3 −7            −6 −7      3 −6
              ⎨                A=            Ax =       Ay =
              ⎩ x + 2 y = 11      1 2             11 2       1 11




Tue, Apr 12
EXAMPLE 2
              Solve the system of equations using Cramer’s rule (matrices).
              ⎧3x − 7 y = −6      3 −7            −6 −7      3 −6
              ⎨                A=            Ax =       Ay =
              ⎩ x + 2 y = 11      1 2             11 2       1 11
                   Ax
              x=
                    A




Tue, Apr 12
EXAMPLE 2
              Solve the system of equations using Cramer’s rule (matrices).
              ⎧3x − 7 y = −6      3 −7            −6 −7      3 −6
              ⎨                A=            Ax =       Ay =
              ⎩ x + 2 y = 11      1 2             11 2       1 11
                   Ax(−6)(2) − (−7)(11)
              x=   =
                 A    (3)(2) − (−7)(1)




Tue, Apr 12
EXAMPLE 2
              Solve the system of equations using Cramer’s rule (matrices).
              ⎧3x − 7 y = −6      3 −7            −6 −7      3 −6
              ⎨                A=            Ax =       Ay =
              ⎩ x + 2 y = 11      1 2             11 2       1 11
                   Ax(−6)(2) − (−7)(11) −12 + 77
              x=   =                   =
                 A    (3)(2) − (−7)(1)   6+7




Tue, Apr 12
EXAMPLE 2
              Solve the system of equations using Cramer’s rule (matrices).
              ⎧3x − 7 y = −6      3 −7            −6 −7      3 −6
              ⎨                A=            Ax =       Ay =
              ⎩ x + 2 y = 11      1 2             11 2       1 11
                   Ax(−6)(2) − (−7)(11) −12 + 77 65
              x=   =                   =        =
                 A    (3)(2) − (−7)(1)   6+7      13




Tue, Apr 12
EXAMPLE 2
              Solve the system of equations using Cramer’s rule (matrices).
              ⎧3x − 7 y = −6      3 −7            −6 −7      3 −6
              ⎨                A=            Ax =       Ay =
              ⎩ x + 2 y = 11      1 2             11 2       1 11
                   Ax(−6)(2) − (−7)(11) −12 + 77 65
              x=   =
                      (3)(2) − (−7)(1)
                                       =
                                         6+7
                                                =                   =5
                 A                                13




Tue, Apr 12
EXAMPLE 2
              Solve the system of equations using Cramer’s rule (matrices).
              ⎧3x − 7 y = −6      3 −7            −6 −7      3 −6
              ⎨                A=            Ax =       Ay =
              ⎩ x + 2 y = 11      1 2             11 2       1 11
                   Ax(−6)(2) − (−7)(11) −12 + 77 65
              x=   =
                      (3)(2) − (−7)(1)
                                       =
                                         6+7
                                                =                   =5
                 A                                13
                        Ay
                 y=
                        A


Tue, Apr 12
EXAMPLE 2
              Solve the system of equations using Cramer’s rule (matrices).
              ⎧3x − 7 y = −6      3 −7            −6 −7      3 −6
              ⎨                A=            Ax =       Ay =
              ⎩ x + 2 y = 11      1 2             11 2       1 11
                   Ax(−6)(2) − (−7)(11) −12 + 77 65
              x=   =
                      (3)(2) − (−7)(1)
                                       =
                                         6+7
                                                =                   =5
                 A                                13
                        Ay
                        (3)(11) − (−6)(1)
                 y=   =
                    A    (3)(2) − (−7)(1)


Tue, Apr 12
EXAMPLE 2
              Solve the system of equations using Cramer’s rule (matrices).
              ⎧3x − 7 y = −6      3 −7            −6 −7      3 −6
              ⎨                A=            Ax =       Ay =
              ⎩ x + 2 y = 11      1 2             11 2       1 11
                   Ax(−6)(2) − (−7)(11) −12 + 77 65
              x=   =
                      (3)(2) − (−7)(1)
                                       =
                                         6+7
                                                =                   =5
                 A                                13
                        (3)(11) − (−6)(1) 33 + 6
                        Ay
                 y=   =                   =
                    A    (3)(2) − (−7)(1)   6+7


Tue, Apr 12
EXAMPLE 2
              Solve the system of equations using Cramer’s rule (matrices).
              ⎧3x − 7 y = −6      3 −7            −6 −7      3 −6
              ⎨                A=            Ax =       Ay =
              ⎩ x + 2 y = 11      1 2             11 2       1 11
                   Ax(−6)(2) − (−7)(11) −12 + 77 65
              x=   =
                      (3)(2) − (−7)(1)
                                       =
                                         6+7
                                                =                   =5
                 A                                13
                        (3)(11) − (−6)(1) 33 + 6 39
                        Ay
                 y=   =                   =      =
                    A    (3)(2) − (−7)(1)   6 + 7 13


Tue, Apr 12
EXAMPLE 2
              Solve the system of equations using Cramer’s rule (matrices).
              ⎧3x − 7 y = −6      3 −7            −6 −7      3 −6
              ⎨                A=            Ax =       Ay =
              ⎩ x + 2 y = 11      1 2             11 2       1 11
                   Ax(−6)(2) − (−7)(11) −12 + 77 65
              x=   =
                      (3)(2) − (−7)(1)
                                       =
                                         6+7
                                                =                   =5
                 A                                13
                        (3)(11) − (−6)(1) 33 + 6 39
                        Ay
                 y=   =                   =      =                =3
                    A    (3)(2) − (−7)(1)   6 + 7 13


Tue, Apr 12
EXAMPLE 2

              ⎧3x − 7 y = −6
              ⎨                  x = 5, y = 3
              ⎩ x + 2 y = 11




Tue, Apr 12
EXAMPLE 2

              ⎧3x − 7 y = −6
              ⎨                  x = 5, y = 3
              ⎩ x + 2 y = 11

                 Check:




Tue, Apr 12
EXAMPLE 2

              ⎧3x − 7 y = −6
              ⎨                       x = 5, y = 3
              ⎩ x + 2 y = 11

                 Check:        3(5) − 7(3) = −6




Tue, Apr 12
EXAMPLE 2

              ⎧3x − 7 y = −6
              ⎨                       x = 5, y = 3
              ⎩ x + 2 y = 11

                 Check:        3(5) − 7(3) = −6
                                15 − 21 = −6




Tue, Apr 12
EXAMPLE 2

              ⎧3x − 7 y = −6
              ⎨                       x = 5, y = 3
              ⎩ x + 2 y = 11

                 Check:        3(5) − 7(3) = −6      5 + 2(3) = 11
                                15 − 21 = −6




Tue, Apr 12
EXAMPLE 2

              ⎧3x − 7 y = −6
              ⎨                       x = 5, y = 3
              ⎩ x + 2 y = 11

                 Check:        3(5) − 7(3) = −6      5 + 2(3) = 11
                                15 − 21 = −6         5 + 6 = 11




Tue, Apr 12
EXAMPLE 2

              ⎧3x − 7 y = −6
              ⎨                       x = 5, y = 3
              ⎩ x + 2 y = 11

                 Check:        3(5) − 7(3) = −6      5 + 2(3) = 11
                                15 − 21 = −6         5 + 6 = 11

                                        (5,3)

Tue, Apr 12
PROBLEM SET




Tue, Apr 12
PROBLEM SET


                                  p. 356 #1-31 odd
                          Solve all using matrices by hand




              “I’m a great believer in luck, and I find the harder I work
                     the more I have of it.” - Thomas Jefferson

Tue, Apr 12

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Int Math 2 Section 8-5

  • 1. SECTION 8-5 Matrices and Determinants Tue, Apr 12
  • 2. ESSENTIAL QUESTIONS How do you find the determinant of a 2X2 matrix? How do you solve systems of equations using determinants? Where you’ll see this: Sports, construction, fitness Tue, Apr 12
  • 3. VOCABULARY 1. Square Matrix: 2. Determinant: 3. Cramer’s Rule: Tue, Apr 12
  • 4. VOCABULARY 1. Square Matrix: A matrix with the same number of rows and columns 2. Determinant: 3. Cramer’s Rule: Tue, Apr 12
  • 5. VOCABULARY 1. Square Matrix: A matrix with the same number of rows and columns ⎡a b ⎤ 2. Determinant: In a 2X2 matrix ⎢ ⎥ , det A = ad - bc. ⎣c d ⎦ 3. Cramer’s Rule: Tue, Apr 12
  • 6. VOCABULARY 1. Square Matrix: A matrix with the same number of rows and columns ⎡a b ⎤ 2. Determinant: In a 2X2 matrix ⎢ ⎥ , det A = ad - bc. ⎣c d ⎦ 3. Cramer’s Rule: A method of using determinants of matrices to solve systems of equations Tue, Apr 12
  • 7. MATRIX m x n: m rows and n columns Tue, Apr 12
  • 8. MATRIX m x n: m rows and n columns ⎡ −2 2 3 ⎤ ⎡3 −1⎤ ⎢ ⎥ ⎢ ⎥ ⎡4 −3 0 ⎤ ⎣ ⎦ ⎣ 9 6 −3 ⎦ ⎣5 8 ⎦ Tue, Apr 12
  • 9. MATRIX m x n: m rows and n columns ⎡ −2 2 3 ⎤ ⎡3 −1⎤ ⎢ ⎥ ⎢ ⎥ ⎡4 −3 0 ⎤ ⎣ ⎦ ⎣ 9 6 −3 ⎦ ⎣5 8 ⎦ 2X3 Tue, Apr 12
  • 10. MATRIX m x n: m rows and n columns ⎡ −2 2 3 ⎤ ⎡3 −1⎤ ⎢ ⎥ ⎢ ⎥ ⎡4 −3 0 ⎤ ⎣ ⎦ ⎣ 9 6 −3 ⎦ ⎣5 8 ⎦ 2X3 2X2 Tue, Apr 12
  • 11. MATRIX m x n: m rows and n columns ⎡ −2 2 3 ⎤ ⎡3 −1⎤ ⎢ ⎥ ⎢ ⎥ ⎡4 −3 0 ⎤ ⎣ ⎦ ⎣ 9 6 −3 ⎦ ⎣5 8 ⎦ 2X3 2X2 1X3 Tue, Apr 12
  • 12. DETERMINANT a b det A = = ad − bc c d Tue, Apr 12
  • 13. EXAMPLE 1 ⎡0 4 ⎤ Find the determinant of ⎢ ⎥. ⎣6 7 ⎦ Tue, Apr 12
  • 14. EXAMPLE 1 ⎡0 4 ⎤ Find the determinant of ⎢ ⎥. ⎣6 7 ⎦ ad − bc Tue, Apr 12
  • 15. EXAMPLE 1 ⎡0 4 ⎤ Find the determinant of ⎢ ⎥. ⎣6 7 ⎦ ad − bc = 0(7) − 4(6) Tue, Apr 12
  • 16. EXAMPLE 1 ⎡0 4 ⎤ Find the determinant of ⎢ ⎥. ⎣6 7 ⎦ ad − bc = 0(7) − 4(6) = 0 − 24 Tue, Apr 12
  • 17. EXAMPLE 1 ⎡0 4 ⎤ Find the determinant of ⎢ ⎥. ⎣6 7 ⎦ ad − bc = 0(7) − 4(6) = 0 − 24 = −24 Tue, Apr 12
  • 19. CRAMER’S RULE 1. Make sure equations look like Ax + By = C. Tue, Apr 12
  • 20. CRAMER’S RULE 1. Make sure equations look like Ax + By = C. 2. Make a 2X2 determinant matrix: x in 1st column, y in 2nd, call A. Tue, Apr 12
  • 21. CRAMER’S RULE 1. Make sure equations look like Ax + By = C. 2. Make a 2X2 determinant matrix: x in 1st column, y in 2nd, call A. 3. Make a new 2X2 determinant matrix: Replace x column with equation answers, call Ax. Tue, Apr 12
  • 22. CRAMER’S RULE 1. Make sure equations look like Ax + By = C. 2. Make a 2X2 determinant matrix: x in 1st column, y in 2nd, call A. 3. Make a new 2X2 determinant matrix: Replace x column with equation answers, call Ax. 4. Make another 2X2 determinant matrix: Replace y column with equation answers, call Ay. Tue, Apr 12
  • 24. CRAMER’S RULE 5. Divide Ax by A and Ay by A. Tue, Apr 12
  • 25. CRAMER’S RULE 5. Divide Ax by A and Ay by A. 6. Check answer and rewrite solution. Tue, Apr 12
  • 26. EXAMPLE 2 Solve the system of equations using Cramer’s rule (matrices). ⎧3x − 7 y = −6 ⎨ ⎩ x + 2 y = 11 Tue, Apr 12
  • 27. EXAMPLE 2 Solve the system of equations using Cramer’s rule (matrices). ⎧3x − 7 y = −6 3 −7 ⎨ A= ⎩ x + 2 y = 11 1 2 Tue, Apr 12
  • 28. EXAMPLE 2 Solve the system of equations using Cramer’s rule (matrices). ⎧3x − 7 y = −6 3 −7 −6 −7 ⎨ A= Ax = ⎩ x + 2 y = 11 1 2 11 2 Tue, Apr 12
  • 29. EXAMPLE 2 Solve the system of equations using Cramer’s rule (matrices). ⎧3x − 7 y = −6 3 −7 −6 −7 3 −6 ⎨ A= Ax = Ay = ⎩ x + 2 y = 11 1 2 11 2 1 11 Tue, Apr 12
  • 30. EXAMPLE 2 Solve the system of equations using Cramer’s rule (matrices). ⎧3x − 7 y = −6 3 −7 −6 −7 3 −6 ⎨ A= Ax = Ay = ⎩ x + 2 y = 11 1 2 11 2 1 11 Ax x= A Tue, Apr 12
  • 31. EXAMPLE 2 Solve the system of equations using Cramer’s rule (matrices). ⎧3x − 7 y = −6 3 −7 −6 −7 3 −6 ⎨ A= Ax = Ay = ⎩ x + 2 y = 11 1 2 11 2 1 11 Ax(−6)(2) − (−7)(11) x= = A (3)(2) − (−7)(1) Tue, Apr 12
  • 32. EXAMPLE 2 Solve the system of equations using Cramer’s rule (matrices). ⎧3x − 7 y = −6 3 −7 −6 −7 3 −6 ⎨ A= Ax = Ay = ⎩ x + 2 y = 11 1 2 11 2 1 11 Ax(−6)(2) − (−7)(11) −12 + 77 x= = = A (3)(2) − (−7)(1) 6+7 Tue, Apr 12
  • 33. EXAMPLE 2 Solve the system of equations using Cramer’s rule (matrices). ⎧3x − 7 y = −6 3 −7 −6 −7 3 −6 ⎨ A= Ax = Ay = ⎩ x + 2 y = 11 1 2 11 2 1 11 Ax(−6)(2) − (−7)(11) −12 + 77 65 x= = = = A (3)(2) − (−7)(1) 6+7 13 Tue, Apr 12
  • 34. EXAMPLE 2 Solve the system of equations using Cramer’s rule (matrices). ⎧3x − 7 y = −6 3 −7 −6 −7 3 −6 ⎨ A= Ax = Ay = ⎩ x + 2 y = 11 1 2 11 2 1 11 Ax(−6)(2) − (−7)(11) −12 + 77 65 x= = (3)(2) − (−7)(1) = 6+7 = =5 A 13 Tue, Apr 12
  • 35. EXAMPLE 2 Solve the system of equations using Cramer’s rule (matrices). ⎧3x − 7 y = −6 3 −7 −6 −7 3 −6 ⎨ A= Ax = Ay = ⎩ x + 2 y = 11 1 2 11 2 1 11 Ax(−6)(2) − (−7)(11) −12 + 77 65 x= = (3)(2) − (−7)(1) = 6+7 = =5 A 13 Ay y= A Tue, Apr 12
  • 36. EXAMPLE 2 Solve the system of equations using Cramer’s rule (matrices). ⎧3x − 7 y = −6 3 −7 −6 −7 3 −6 ⎨ A= Ax = Ay = ⎩ x + 2 y = 11 1 2 11 2 1 11 Ax(−6)(2) − (−7)(11) −12 + 77 65 x= = (3)(2) − (−7)(1) = 6+7 = =5 A 13 Ay (3)(11) − (−6)(1) y= = A (3)(2) − (−7)(1) Tue, Apr 12
  • 37. EXAMPLE 2 Solve the system of equations using Cramer’s rule (matrices). ⎧3x − 7 y = −6 3 −7 −6 −7 3 −6 ⎨ A= Ax = Ay = ⎩ x + 2 y = 11 1 2 11 2 1 11 Ax(−6)(2) − (−7)(11) −12 + 77 65 x= = (3)(2) − (−7)(1) = 6+7 = =5 A 13 (3)(11) − (−6)(1) 33 + 6 Ay y= = = A (3)(2) − (−7)(1) 6+7 Tue, Apr 12
  • 38. EXAMPLE 2 Solve the system of equations using Cramer’s rule (matrices). ⎧3x − 7 y = −6 3 −7 −6 −7 3 −6 ⎨ A= Ax = Ay = ⎩ x + 2 y = 11 1 2 11 2 1 11 Ax(−6)(2) − (−7)(11) −12 + 77 65 x= = (3)(2) − (−7)(1) = 6+7 = =5 A 13 (3)(11) − (−6)(1) 33 + 6 39 Ay y= = = = A (3)(2) − (−7)(1) 6 + 7 13 Tue, Apr 12
  • 39. EXAMPLE 2 Solve the system of equations using Cramer’s rule (matrices). ⎧3x − 7 y = −6 3 −7 −6 −7 3 −6 ⎨ A= Ax = Ay = ⎩ x + 2 y = 11 1 2 11 2 1 11 Ax(−6)(2) − (−7)(11) −12 + 77 65 x= = (3)(2) − (−7)(1) = 6+7 = =5 A 13 (3)(11) − (−6)(1) 33 + 6 39 Ay y= = = = =3 A (3)(2) − (−7)(1) 6 + 7 13 Tue, Apr 12
  • 40. EXAMPLE 2 ⎧3x − 7 y = −6 ⎨ x = 5, y = 3 ⎩ x + 2 y = 11 Tue, Apr 12
  • 41. EXAMPLE 2 ⎧3x − 7 y = −6 ⎨ x = 5, y = 3 ⎩ x + 2 y = 11 Check: Tue, Apr 12
  • 42. EXAMPLE 2 ⎧3x − 7 y = −6 ⎨ x = 5, y = 3 ⎩ x + 2 y = 11 Check: 3(5) − 7(3) = −6 Tue, Apr 12
  • 43. EXAMPLE 2 ⎧3x − 7 y = −6 ⎨ x = 5, y = 3 ⎩ x + 2 y = 11 Check: 3(5) − 7(3) = −6 15 − 21 = −6 Tue, Apr 12
  • 44. EXAMPLE 2 ⎧3x − 7 y = −6 ⎨ x = 5, y = 3 ⎩ x + 2 y = 11 Check: 3(5) − 7(3) = −6 5 + 2(3) = 11 15 − 21 = −6 Tue, Apr 12
  • 45. EXAMPLE 2 ⎧3x − 7 y = −6 ⎨ x = 5, y = 3 ⎩ x + 2 y = 11 Check: 3(5) − 7(3) = −6 5 + 2(3) = 11 15 − 21 = −6 5 + 6 = 11 Tue, Apr 12
  • 46. EXAMPLE 2 ⎧3x − 7 y = −6 ⎨ x = 5, y = 3 ⎩ x + 2 y = 11 Check: 3(5) − 7(3) = −6 5 + 2(3) = 11 15 − 21 = −6 5 + 6 = 11 (5,3) Tue, Apr 12
  • 48. PROBLEM SET p. 356 #1-31 odd Solve all using matrices by hand “I’m a great believer in luck, and I find the harder I work the more I have of it.” - Thomas Jefferson Tue, Apr 12