Solving a system of equations with 3 unknowns

mkaynutty

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Dec 15, 2011
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3x+2y+2z=9
2x-y+2z=2
x+5y-6z=-14

So I have the concept down on how to solve it but when I do it my numbers aren't coming out right.
I chose to solve for y and ended up with the two equations:

7x+6z=13
11x+4z=-4

I know I'm supposed to continue it out as if it were a two system but elimination doesn't work and when I do substitution it doesn't give me the correct answer.
Can anyone tell me what I'm doing wrong?
 
3x+2y+2z=9
2x-y+2z=2
x+5y-6z=-14

So I have the concept down on how to solve it but when I do it my numbers aren't coming out right.
I chose to solve for y and ended up with the two equations:

7x+6z=13
11x+4z=-4

I know I'm supposed to continue it out as if it were a two system but elimination doesn't work and when I do substitution it doesn't give me the correct answer.
Can anyone tell me what I'm doing wrong?

Your first steps look okay. Show us your work, and we'll be happy to look it over.

You mention the "correct answer". What is the correct answer that you have been given?
 
3x+2y+2z=9
2x-y+2z=2
x+5y-6z=-14

So I have the concept down on how to solve it but when I do it my numbers aren't coming out right.
I chose to solve for y and ended up with the two equations:

7x+6z=13
11x+4z=-4

I know I'm supposed to continue it out as if it were a two system but elimination doesn't work and when I do substitution it doesn't give me the correct answer.
Can anyone tell me what I'm doing wrong?

77x + 66z = 143
77x + 28z = -28

subtracting

38 z = 171 → z = 4.5

x = 1/7 * (13 - 4.5*6)) = -1/7 * 14= - 2

If you written the problem correctly - these should be part of the answers.
 
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