Answer
-$\frac{2}{9}$$a^{2}$$b^{5}$
Work Step by Step
(-$\frac{7}{12}$$a^{2}b$)($\frac{8}{21}$$b^{4}$) =
Use the exponent rule to simplify: $b^{n}$ $b^{m}$ = $b^{m+n}$
-$\frac{7}{12}$ $\times$ $\frac{8}{21}$ $\times$ $a^{2}$ $\times$ $b^{1+4}$ =
-$\frac{2}{9}$ $\times$ $a^{2}$ $\times$ $b^{5}$ =
-$\frac{2}{9}$$a^{2}$$b^{5}$
