Tính: a) 6/13. 8/7 . -26/3 . -7/8; b) 6/5 . 3/13 - 6/5 . 16/13

* Hướng dẫn giải

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

= $\frac{6}{13}.\frac{-26}{3}.\frac{8}{7}.\frac{-7}{8}$ (tính chất giao hoán)

= $\frac{6.\left(-26\right)}{13.3}.\frac{8.\left(-7\right)}{7.8}$

= (-4).(-1) = 4

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

= $\frac{6}{5}.\left(\frac{3}{13}-\frac{16}{13}\right)$

= $\frac{6}{5}.\left(\frac{-13}{13}\right)$ = $\frac{-6}{5}$