tolong dibantu ya beserta penjelasannya terimakasih

f(x) = x² - 2x

f(4+h) - f(4) / h =
= {(4+h)² -2(4+h) - (4² - 2(4)} / h
= {16+8h+h² - 8 - 2h - 16 + 8) /(h)
= (h² + 6h)/(h)
= h(h+6)/h
= h + 6