Đáp án:
a, ,$\frac{-7}{5}$
b,$\frac{-122}{15}$
c,-5
Giải thích các bước giải:
a,$\frac{3}{13}$ - $\frac{21}{84}$ + - $\frac{16}{13}$ + $\frac{1}{4}$ - $\frac{6}{15}$
= ( $\frac{3}{13}$ - $\frac{16}{13}$ ) + ( $\frac{1}{4}$ - $\frac{21}{84}$ ) - $\frac{6}{15}$
= -1 + 0 - $\frac{6}{15}$
= $\frac{-7}{5}$
b,$\frac{4}{15}$×$\frac{31}{2}$ - $\frac{4}{5}$× $\frac{46}{3}$
= $\frac{4×2}{15×2}$×$\frac{31×15}{2×15}$ - $\frac{4×6}{5×6}$× $\frac{46×10}{3×10}$
= $\frac{8}{30}$×$\frac{465}{30}$ - $\frac{24}{30}$× $\frac{460}{30}$
= $\frac{62}{15}$ - $\frac{184}{15}$
= ,$\frac{-122}{15}$
c,$\frac{-1}{4}$×$\frac{152}{11}$ - $\frac{1}{4}$× $\frac{68}{11}$
= $\frac{-1}{4}$ × ( $\frac{152}{11}$ + $\frac{68}{11}$ )
= $\frac{-1}{4}$ × 20
= -5
