Đáp án:
a) $\frac{-11}{20}$
b) $\frac{-2}{3}$
c) $\frac{29}{42}$
Giải thích các bước giải:
a) $\frac{2}{5}$ . $\frac{-7}{8}$ - $\frac{1}{5}$
= ( $\frac{2}{5}$ . $\frac{-7}{8}$ ) - $\frac{1}{5}$
= $\frac{-7}{20}$ - $\frac{1}{5}$
= $\frac{-35}{100}$ - $\frac{20}{100}$
= $\frac{-55}{100}$
= $\frac{-11}{20}$
b) 3 . $\frac{-1}{3}$$^{3}$ + $\frac{1}{3}$
= 3 . $\frac{-1}{3}$ + $\frac{1}{3}$
= ( 3 . $\frac{-1}{3}$ ) + $\frac{1}{3}$
= -1 + $\frac{1}{3}$
= $\frac{-3}{3}$ + $\frac{1}{3}$
= $\frac{-2}{3}$
c) $\frac{1}{7}$ - $\frac{-3}{14}$ + $\frac{1}{3}$
= ( $\frac{1}{7}$ - $\frac{-3}{14}$ ) + $\frac{1}{3}$
= ( $\frac{14}{98}$ - $\frac{-21}{98}$ ) + $\frac{1}{3}$
= $\frac{35}{98}$ + $\frac{1}{3}$
= $\frac{105}{294}$ + $\frac{98}{294}$
= $\frac{203}{294}$
= $\frac{29}{42}$
