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8 February, 13:13

2x - 3y - 9z = 11

3x + 3z = - 5

-3x + y - 4z = 8

solve for x, y, z

+4
Answers (2)
  1. 8 February, 13:23
    0
    x = 0, y = 1.333, z = - 1.667 (to the nearest thousandth).

    Step-by-step explanation:

    2x - 3y - 9z = 11 A

    3x + 3z = - 5 B

    -3x + y - 4z = 8 C

    Multiply Equation C by 3:

    -9x + 3y - 12z = 24 D

    Adding A + D:

    -7x - 21z = 35 Divide by 7:

    -x - 3z = 5 E

    Adding B + E:

    2x = 0

    x = 0

    Plugging in x = 0 into equation B:

    3 (0) + 3z = - 5

    z = - 5/3

    z = - 1.667

    Now plugging the values of y and z into equation A:

    2 (0) - 3y - 9 (-5/3) = 11

    -3y = 0 + 11 + 9 (-5/3) = - 4

    y = 4/3 = 1.333.
  2. 8 February, 13:37
    0
    Step-by-step explanation:

    2x - 3y - 9z = 11 ... (1)

    3x + 3z = - 5 ... (2)

    -3x + y - 4z = 8 ... (3)

    add (3) and (2) : y - z = 3 so : y = z+3 (*)

    put this value in (1) : 2x-3 (z+3) - 9z = 11

    2x-3z - 9-9z = 11 so : 2x = 12z+20

    x = 6z+10 ... (**)

    put this value in (2) : 3 (6z+10) + 3z = - 5

    18z+30+3z=-5

    21z = - 35

    z = - 35/21 = - 5/3

    put this value in (*) and (**) you have x and y.
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