Posted by **Linda** on Tuesday, November 1, 2011 at 2:19am.

Solve the system using any algebraic method.

2x - 2y + z = 3

5y - z = -31

x + 3y + 2z = -21

______________________

The answer I got for this is ( -26, 6,67) but I know its wrong and I don't know why. Help please >< my work is at the bottom

I used substitution method changed 5y-z=-31 to z=5y+31 then I:

Plugged it in the first equation=

2x-2y+5y+31=3 -> 2x+3y+31=3 -> 2x+3y=-28 is my new 1st equation...

Plugged in z=5y+31 to equation 3 =

x+3y+2(5y+31)=-21 -> x+3y+10y+62=-21 -> x+13y+62=-21 -> x+13y=-83 is my new 2nd equation.

2(=13y=82)+3y=-28 -> -26-166+3y=-28 -> -23y=138 - > y=6

2x+3(6)=-28 -> 2x+18=-28 -> 2x=-46 -> x=-23

2(-26)-2*6)+z=3 -> -52-12+z=3 -> -64+z=3 -> z=67

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