Trả lời Luyện tập 2 trang 20

Đề bài

Tính:

a)$\frac{6}{13}.\frac{8}{7}.\frac{-26}{3}.\frac{-7}{8}$

b) $\frac{6}{5}.\frac{3}{13}-\frac{6}{5}.\frac{16}{13}$

Lời giải chi tiết

a) $\frac{6}{13}.\frac{8}{7}.\frac{-26}{3}.\frac{-7}{8}$

$\begin{array}{c}=\left(\frac{6}{13}.\frac{-26}{3}\right).\left(\frac{8}{7}.\frac{-7}{8}\right)\\ =\frac{6.\left(-26\right)}{13.3}.\frac{8.\left(-7\right)}{7.8}\\ =(-4).\left(-1\right)=4\end{array}$

b) $\frac{6}{5}.\frac{3}{13}-\frac{6}{5}.\frac{16}{13}$

$\begin{array}{c}=\frac{6}{5}.\left(\frac{3}{13}-\frac{16}{13}\right)\\ =\frac{6}{5}.\frac{3-16}{13}\\ =\frac{6}{5}.\frac{-13}{13}\\ =\frac{6}{5}.\left(-1\right)\\ =\frac{-6}{5}\end{array}$