Tính a) (-2 1/5) . (-9/11) . (-1 1/14) . 2/5 b) (-5 1/2) . (-1/2) - 2/3 . (-2/3)

* Hướng dẫn giải

a) 

$\begin{array}{l}\left(-2\frac{1}{5}\right).\left(-\frac{9}{11}\right).\left(-1\frac{1}{14}\right).\frac{2}{5}\\ =\left(-\frac{11}{5}\right).\left(-\frac{9}{11}\right).\left(-\frac{15}{14}\right).\frac{2}{5}\\ =-\frac{27}{35}\end{array}$

b)

$\begin{array}{l}\left(-5\frac{1}{2}\right).\left(-\frac{1}{2}\right)-\frac{2}{3}.\left(-\frac{2}{3}\right)\\ =\left(-\frac{11}{2}\right).\left(-\frac{1}{2}\right)+\frac{4}{9}=\frac{11}{4}+\frac{4}{9}\\ =\frac{115}{36}\end{array}$