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.
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You have z = -2 from eqn 1 & 2.
4z = -8
z = -2
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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.