Đề bài

Tính: a) \(\dfrac{{ - 2}}{5}.\dfrac{5}{4}\) b) \(\dfrac{{ - 7}}{{10}}.\dfrac{{ - 9}}{{11}}\)

Lời giải chi tiết

a) \(\dfrac{{ - 2}}{5}.\dfrac{5}{4}\)\( = \dfrac{{ - 2.5}}{{5.4}} = \dfrac{{ - 10}}{{20}} = \dfrac{{ - 10:10}}{{20:10}} = \dfrac{{ - 1}}{2}\)b) \(\dfrac{{ - 7}}{{10}}.\dfrac{{ - 9}}{{11}}\)\( = \dfrac{{ - 7.\left( { - 9} \right)}}{{10.11}} = \dfrac{{63}}{{110}}\)