f(x) = x2 − 2x + 9,

f(5 + h) − f(5)
h
, h ≠ 0

f(5+h) = (5+h)^2 - 2(5+h) + 9 = h^2+8h+24

f(5) = 5^2 - 2*5 + 9 = 24
now finish it off