Nhân các phân số:

- Hướng dẫn giải

$\begin{array}{l}a)\frac{-1}{3}.\frac{5}{97}=\frac{(-1).5}{3.9}=\frac{-5}{27}.\\ \\ b)\frac{-3}{7}.\frac{5}{15}=\frac{(-3).5}{7.15}=\frac{-1}{7}.\\ \\ c)\frac{-7}{3}.\frac{9}{21}=\frac{(-7).9}{3.21}=-1.\\ \\ d\left)\right(-3).\frac{7}{24}=\frac{(-3).7}{24}=\frac{-7}{8}.\\ \\ e\left)\frac{-5}{3}\begin{array}{cccc}& & & \end{array}g\right)\frac{-25}{11}\\ \\ h)14.\\ \\ i)\frac{-12}{7}\end{array}$