f'(c)=[ f(b)-f(a) ] / b-a in interval [a,b]
find f(2) or f(a) and find f(8) or f(b)
plug it into f'(c) that is above
once you find that find f'(x) and set it equal to f'(c) that you found in the previous step solve for x, or replace with c and that is your answer
