# How do you factor (1/3)(pi)(r^2)(h) + (1/3)(pi)(R^2)(h) ?

$\frac{1}{3} \pi h \left({r}^{2} + {R}^{2}\right)$
Separate the common factors, $\frac{1}{3} , \pi \mathmr{and} h$ and write the remaining terms, ${r}^{2} \mathmr{and} {R}^{2}$ in the bracket with the correct sign in between.
$= \frac{1}{3} \pi h \left({r}^{2} + {R}^{2}\right)$