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16 December, 02:30

Solve the system by substitution

-x - y - z = - 8

-4x + 4y + 5z = 7

2x + 2z = 4

+1
Answers (1)
  1. 16 December, 05:45
    0
    First:

    2x + 2z = 4

    2 (x+z) = 4

    x+z=4/2

    x=2-z

    -x - y - z = - 8

    - (2-z) - y-z = - 8 replace x

    -2+z-y-z = - 8 (cancel z)

    -2-y = - 8

    6 = y

    Then:

    -4x + 4y + 5z = 7 replace x and y

    -4 (2-z) + 4*6 + 5z = 7

    -8 + 4z + 24 + 5z = 7

    16 + 9z = 7

    9z = 7 - 16

    9z = - 9

    z = - 9/9

    z = - 1

    Finally

    x = 2-z replace z

    x = 2 - (-1)

    x = 3
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