Answer
$h^2+3a^2+3ah$
Work Step by Step
f(x)=$x^{3}$
Lets Evaluate:
$\frac{f(a+h)-f(a)}{h}$ = $\frac{(a+h)^{3}-a^{3}}{y}$ $\frac{a^3+h^3+3a^2h+3ah^2-a^3}{h}$ = $\frac{h^3+3a^2h+3ah^2}{h}$ = $\frac{h(h^2+3a^2+3ah)}{h}$ = $h^2+3a^2+3ah$
Formulas Used: $(a+b)^3$ = $a^3+b^3+3a^2b+3ab^2$
