$f'(a) = \lim_{h \to 0} \frac{f(a+h) - f(a)}{h}$

$f'(a) = \lim_{h \to 0} \frac{f(a+h) + f(a)}{h}$

$f'(a) = \frac{f(a+1) - f(a)}{1}$

$f'(a) = f(a)$