Tolong bantu plis fast respon ya

[tex]\displaystyle \frac{r(x+h)-r(x)}{h}=\frac{(x+h)^2+2h(x+h)+h^2-x^2-2hx-h^2}{h}\\\frac{r(x+h)-r(x)}{h}=\frac{x^2+2hx+h^2+2hx+2h^2-x^2-2hx}{h}\\\frac{r(x+h)-r(x)}{h}=\frac{3h^2+2hx}{h}\\\\\boxed{\boxed{\frac{r(x+h)-r(x)}{h}=3h+2x}}[/tex]