Solving simultaneous equations.

Hey guys,

This problem has been driving me crazy: If 2x - y = 9 and 3x + 4y = -14, then x = ? and y = ?

I keep getting y = -9 and x = 7.33 by doing this:

2x - y = 9 -> 2x - 9 = y -> 2(0) - 9 = y -> -9 = y

then

3x + 4(-9) = -14 -> 3x + -36 = -14 -> 3x = 22 -> x = 7.33

I know these are wrong, though. Would anyone be able to tell me what's wrong?

Thanks in advance!

Re: Basic algebra problem

hi

you cannot assume that x=0,because if it isn't it is going to give you wrong answers.

you can try doing something like this:

2x-y=9

-y=9-2x

y=-9+2x

y=2x-9

we substitute into the second equation:

3x+4(2x-9)=-14

3x+8x-36=--14

11x=36-14

11x=22

x=2

can you find y now?