Question 1054712
f(x)=(5x-x^2)/h
f(5+h)=5(5+h)-(5+h)^2
=25+5h-25-10h-h^2
subtract f(5), which is 25-25 or 0
25+5h-25-10h-h^2-0=5h-10h-h^2
divide that by h and have -5-h.
Check
Using calculus, the derivative of this function is 5-2x.  Evaluated at 5, the result is 5-10=-5, and as h approaches 0, the value -5-h approaches -5.