Question

Solve the linear system of equations using the linear combination method. {8a−4b=205a−8b=62

Answer 1

Sorry I am a little late...

a = -2

b = -9

Here is how to solve the problem. 

First thing I did was multiply the first equation by -2 so that we can eliminate the the b. After you multiply it by -2, your new equation is -16a + 8b = -40. 

You leave the second equation alone and all you do is combine like terms. So -16a+5a is -11. And you eliminate the b. Then you're going to do -40+62 which is 22. So it's -11a=22 and then you have to solve for a. What I did was I multiplied the whole thing by minus to turn the a positive. So then it's 11a=-22. Pretty easy, the final step is to simplify. -22/11 is -2. ;D 

So there you have your first answer. 

a = -2 

Now we're going to use the first answer to help us find b. 

For the second equation, all you're going to do is plug in that a. 

5 (-2)-8b=62 

-10 - 8b = 62

Now we move the -10 to the other side...

-8b = 62 + 10 

-8b = 72

Multiply the whole thing by negative once again to turn the b positive.

Now we have 8b = -72 

The final step is to simplify. -72/11 = -9

b = -9 

Hope this makes sense! Also I had the same question on my test and I got it right. :)