algebra

Solve the following system of equations:


x + 2y - z = 2
-3x + y + z = -9
x + y - 2z = 5

I came up with
(-2,-11/3, -2)
Is this correct?

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  1. No,
    had you simply substituted your answer into the 1st equation, you would have seen that it was not correct

    Add the 1st and 2nd ---> -2x+3y = -7 , (#4)
    double the 2nd , then add to the 3rd ---> -5x +3y =-13 , (#5)

    #4 - #5 :
    3x = 6
    x = 2

    sub back into #4
    -4 + 3y = -7
    3y = -3
    y = -1

    back into 1st :
    2 - 2 - z =2
    -z = 2
    z = -2

    so (2,-1,-2)

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