jika f(x) =x2+3 maka lim f(x+h) -f(x) /h adalah

f(x) = x² + 3
f(x + h)= (x + h)² + 3 = x² + 2hx + h² + 3
lim h→0 [f(x + h) - f(x)]/h 
limit gk sy ditulis
= [x² + 2hx + h² + 3 - (x² + 3)]/h
= (x² + 2hx + h² + 3 - x² - 3)/h
= (2hx + h²)/h
= h(2x + h)/h
= 2x + h
substitusi h→0
= 2x + 0
= 2x