Question

Não consigo resolver me ajudem por favor

Answer 1

$\dfrac{r^{3}-2r^{2}s+rs^{2}}{2(r-s)} = \dfrac{r (r^{2}-2rs+s^{2})}{2 (r-s)} = \dfrac{r (r-s). (r-s))}{2(r-s)} = \dfrac{r^{2}-rs}{2}$