It's not up to the forum members to do the math for you.
If you show some workings we may then show you where to improve
For the first one. Expand this out.
For the second one note that
a) f(x) = 4 - 3x - x^2
Diff. Quotient : ( f(3+h) - f(3) ) / h
b) f(x) = (x+8) / (x+6)
Diff. Quotient : ( f(x) - f(6) ) / x-6
I understand how to do the problem, but for some reason I just can't get the right answer. I have come up with four different ones. Can someone do the math here for me? I can't see what I am doing wrong. If I have to, I'll post my work.