Question

Solve the following system of equations:

x + 3y - z = 2
x - 2y + 3z = 7
x + 2y - 5z = -21

(2, 3, 5)
(-2, 3, 5)
(2, -3, 5)
(2, 3, -5)
@SolomonZelman @phi

Answer 1

use elimination. write just the coefficients (remember the order will represent x,y,z):
1 3 -1 2
1 -2 3 7
1 2 -5 -21

the first step is multiply the first row by -1 and add to the second row
e.g. -1 -3 + 1 -2 is the first row multiplied by -1
add 1 -2 3 7 (this is the second row)
-------------------
0 -5 4 5 this is the new second row.

Answer 2

1 3 -1 2
0 -5 4 5
1 2 -5 -21

now do the same thing with the third row: multiply the first row by -1 and add to the last row. the idea is that the first column will have 0's (except for the first row)

Answer 3

can you do this next step: multiply the first row by -1, add that to the last row, and make the answer the new last row ?

Answer 4

@ganeshie8

Answer 5

@SolomonZelman

Answer 6

@iambatman