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Anonymous
Anonymous asked in Science & MathematicsMathematics · 9 years ago

use matrix to solve the system of equations?

how would you set up the matrix to solve

6x+5y=21

5x-4y=42

can someone please help me out? please and thank you:)

1 Answer

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  • cidyah
    Lv 7
    9 years ago
    Favorite Answer

    6 5

    5 -4

    is the coefficient matrix

    Find its inverse.

    Its determinant is (6)(-4) -(5)(5) = -24-25=-49

    inverse of

    a b

    c d

    is

    d/k -b/k

    -c/k a/k

    where k=-49

    6 5

    5 -4

    Find the inverse:

    [ -4/-49 5/49]

    [5/49 -6/49] ---------------(1)

    Multiply by

    21

    42 -------------(2)

    [ -4/-49 5/49] [21]

    [5/49 -6/49] [42]

    x = (4/49)(21)+(5/49)(42) = 6

    y = (5/49)(21)-(6/49)(42) = -3

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