SOLUTION: Solve. 2x - y - 3z = -1 2x - y + z = -9 x + 2y - 4z = 17 I got so far as; 2x - y - 3z = -1 4z = -8 3y - 5z = 35 Please help.

Algebra ->  Coordinate Systems and Linear Equations -> SOLUTION: Solve. 2x - y - 3z = -1 2x - y + z = -9 x + 2y - 4z = 17 I got so far as; 2x - y - 3z = -1 4z = -8 3y - 5z = 35 Please help.      Log On


   

Question 639160: Solve.
2x - y - 3z = -1
2x - y + z = -9
x + 2y - 4z = 17
I got so far as;
2x - y - 3z = -1
4z = -8
3y - 5z = 35
Please help.
Found 2 solutions by Tatiana_Stebko, Alan3354:
Answer by Tatiana_Stebko(1539) About Me  (Show Source):
You can put this solution on YOUR website!
system%282x+-+y+-+3z+=+-1%2C+2x+-+y+%2B+z+=+-9%2Cx+%2B+2y+-+4z+=+17%29
Multiply the third equation by 2
system%282x+-+y+-+3z+=+-1%2C+2x+-+y+%2B+z+=+-9%2C2x+%2B+4y+-+8z+=+34%29
Subtract the first equation from the second and from the third equations
system%282x+-+y+-+3z+=+-1%2C+4z+=+-8%2C+5y+-+5z+=+35%29
From the second equationz=-2
Substitute z=-2 into the third equation
5y%2B10=35
5y=25
y=5
Substitute z=-2%2C+y=5 into the first equation
2x-5%2B6=-1
2x=-2
x=-1
Answer: system%28x=-1%2C+y=5%2C+z=-2%29

Answer by Alan3354(69443) About Me  (Show Source):
You can put this solution on YOUR website!
Solve.
2x - y - 3z = -1
2x - y + z = -9
x + 2y - 4z = 17
I got so far as;
2x - y - 3z = -1
4z = -8
3y - 5z = 35
Please help.
==================
You have z = -2 from eqn 1 & 2.
4z = -8
z = -2
--------
3y - 5z = 35 **** I don't know about that.
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2x - y + z = -9
x + 2y - 4z = 17
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2x - y + z = -9
2x + 4y -8z = 34 times 2
------------------ Subtract
-5y + 9z = -43
Sub for z
-5y - 18 = -43
y = 5
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Sub for y & z in any eqn to find x.