Pretty sure f(b) - f(a) equals 7/15 here. When you divide by (b-a), you get 1/15.
The derivative looks good.
I hope this helps! Good luck!
f(x) = x / (x+ 4) [1,8]
I found fprime(x) to be 4/(x+4)^2
Then I used (f(b) - f(a)) / (b -a) and found that to be 7/15
I set the equation to zero to solve for c and my answer comes out wrong. (squarroot60/7)-4
PS How do I use the math syntax keys on this forum?