Answer:
12x² + 12xh + 4h² - 5
Explanation:
f(x + h) - f(x) / h
= [4(x + h)³ - 5(x + h)] - [4x³ - 5x] / h
= [4x³ + 12x²h + 12xh² + 4h³ - 5x - 5h] - [4x³ - 5x] / h
= 4x³ + 12x²h + 12xh² + 4h³ - 5x - 5h - 4x³ + 5x / h
= 12x²h + 12xh² + 4h³ - 5h / h
= 12x² + 12xh + 4h² - 5
Hope this helps :)