Please answer the following question?

(a)
f(x) = (x² - 4)²
f(2 + h) = [(2 + h)² - 4]² = (2² + 2×2×h + h² - 4)² = (4h + h²)² = [h(4 + h)]² = h²(4 + h)².

(b)
f'(2)
= lim{h→0} [f(2 + h) - f(2)]/h
= lim{h→0} [h²(4 + h)² - (2² - 4)²]/h
= lim{h→0} [h²(4 + h)²]/h
= lim{h→0} h(4 + h)²
= 0 × 4²
= 0