SOLUTION: How to solve this? y=-4 -2x-4y+4z=20 -2x-2y-3z=26 Struggling here..

Question 1090922: How to solve this?
y=-4
-2x-4y+4z=20
-2x-2y-3z=26
Struggling here..
Answer by Edwin McCravy(20055) (Show Source): You can put this solution on YOUR website!
y=-4
-2x-4y+4z=20
-2x-2y-3z=26

Substitute -4 for y in the other two equations:

-2x-4(-4)+4z = 20
   -2x+16+4z = 20
      -2x+4z = 4

-2x-2(-4)-3z = 26
    -2x+8-3z = 26
      -2x-3z = 18

Solve the system:

      -2x+4z = 4
      -2x-3z = 18

Multiply the top equation by -1
and add the two equations:

       2x-4z = -4
      -2x-3z = 18
     -------------
         -7z = 14
           z = -2

Substitute in 

      -2x+4z = 4
   -2x+4(-2) = 4
       -2x-8 = 4
         -2x = 12
           x = -6

So the solution is

(x, y, z) = (-6, -4, -2)

Edwin

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