# Thread: Need help solving this Simultaneous Equation

1. ## Need help solving this Simultaneous Equation

Okay I have these

A+B = 5
4A+ -2/3B = -8

I have a rough idea of what the answer is and my answers are no where near it; this is what I have

Times A+B = 5 by 2
Times 4A + -2/3B = -8 by 3

2A + 2B = 10
12A + -2B = -24

14A = -14
A = -14/14 = -1

is this correct so far?

2. Yes, now substitute A = -1 into one of the equations to get B

3. okay do you get -6

I get this;

12A+-2B = -24
12(-1) + 24 = 2B

12=2B

12/-2 = B

b= -6

4. Originally Posted by oligo
2A + 2B = 10
12A + -2B = -24
This is a small typo - you have obtained the correct result for A.

Edit:

A + B = 5.

If A = -1

-1 + B = 5

Does B = -6?

5. okay think I have it now, answer is +6 correct?

I made the mistake by putting a minus on the 2 here; 12/-2 = B (should be 12/2 = B)

6. Originally Posted by oligo
okay think I have it now, answer is +6 correct?

I made the mistake by putting a minus on the 2 here; 12/-2 = B (should be 12/2 = B)
That's right. Remember that you can (and perhaps, if unsure, should) check by substituting into both equations to make sure you get the same result.