SOLUTION: 3 system.. x+2y+5z= -1 2x-y+z=2 3x+4y-4z=14 HELP ME PLEASE!

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Question 258240: 3 system..
x+2y+5z= -1
2x-y+z=2
3x+4y-4z=14
HELP ME PLEASE!
Answer by Edwin McCravy(20056) About Me  (Show Source):
You can put this solution on YOUR website!

system%28x%2B2y%2B5z=+-1%2C%0D%0A2x-y%2Bz=2%2C%0D%0A3x%2B4y-4z=14%29

Pick a letter and an equation to solve for it in.

I will pick z and the second equation to solve for z in:

2x-y%2Bz=2
z=2-2x%2By

Substitute %282-2x%2By%29 for z in the other two
equations, (but not the same one you just used) 

Substituting it in

x%2B2y%2B5z=-1
x%2B2y%2B5%282-2x%2By%29=-1
x%2B2y%2B10-10x%2B5y=-1
-9x%2B7y%2B10=-1
-9x%2B7y=-11

Substituting it in

3x%2B4y-4z=14
3x%2B4y-4%282-2x%2By%29=14
3x%2B4y-8%2B8x-4y=14
11x-8=14
11x=22
x=2

Now you just have this simple system:

system%28-9x%2B7y=-11%2Cx=2%29

and I'll bet you can finish that by yourself, just by
substituting back

Answer x=2, y=1, z=-1 

Edwin