Question

Please help!!!
solve for A,B,and C

2A+3B-4C=7
A -5B+2C=2
-7A-3B+C=-20

Answer 1

solve it simultaneously by elimination method or substitution! :-)

Answer 2

I did but my could not get the same answer that my prof. gave me. His answer (1,-1,-2)
I tested his answer but the last equation seems not work out

Answer 3

can you show me the solution of your professor?

Answer 4

By the way, I missing, let me retype my question:
2A+3B-4C=7
A-5B+2C=2
-7A-3B+5C=-20
and his answer is (1,-1,-2)

Answer 5

try this: equation 1 minus equation 2, equation 1 minus equation 3 and equation 2 minus equation 3
1-2: by elimination
13B-8C=3

1-3:
-5A+C=27

2-3:
38B+19C=-6