Actually, I think I may be on my way to answering them both. It's just that I don't know what to do when I get to a certain point. Here goes:

for the y = mx + b problem....

I set it up as

and

.

I set up a matrix that looks like:

4 1 -1

1 1 8

I then set it up in rref form using about 8 steps, until I come out to a matrix that looks like...

1 0 -3

0 1 11

However, I don't really know what this tells me. I don't know how to check it, or set it up in an equation form. I get to the same point in the quadratic problem.