Answer:
8a. 0 8b. -1/3
Step-by-step explanation:
slope formula: 
8a. => (8 + 12)/(17 - 17) = 20/0 = 0
8b. (1 + 2)/(-3 - 6) = 3/-9 = - 1/3
Answer:

Step-by-step explanation:
First, you have to substitute both functions into the equation to get:

Then, you distribute the negative sign in front of g(x) to get:

And finally, you add/subtract the x's that have the same power to get:

Easy if you know the formula
all this means is that your x value is a, and when it is, will give you the value 26.
f(a) = 6a - 4 = 26
6a = 30
a = 5