Bỏ dấu ngoặc rồi tính. a) (-3/7) + (5/6 - 4/7); b) 3/5 - (2/3 + 1/5)

* Hướng dẫn giải

a) $\left(\frac{-3}{7}\right)+\left(\frac{5}{6}-\frac{4}{7}\right)=\frac{-3}{7}+\frac{5}{6}-\frac{4}{7}$

$=\left(\frac{-3}{7}-\frac{4}{7}\right)+\frac{5}{6}=\frac{-7}{7}+\frac{5}{6}$

$=-1+\frac{5}{6}=\frac{-6}{6}+\frac{5}{6}=\frac{-1}{6}$

b) $\frac{3}{5}-\left(\frac{2}{3}+\frac{1}{5}\right)=\frac{3}{5}-\frac{2}{3}-\frac{1}{5}$

$=\left(\frac{3}{5}-\frac{1}{5}\right)-\frac{2}{3}=\frac{2}{5}-\frac{2}{3}$

$=\frac{6}{15}-\frac{10}{15}=\frac{-4}{15}$

c) $\left[\left(\frac{-1}{3}\right)+1\right]-\left(\frac{2}{3}-\frac{1}{5}\right)=\frac{-1}{3}+1-\frac{2}{3}+\frac{1}{5}$

$=\left(\frac{-1}{3}-\frac{2}{3}\right)+1+\frac{1}{5}=\frac{-3}{3}+1+\frac{1}{5}$

$=-1+1+\frac{1}{5}=\frac{1}{5}$

d) $1\frac{1}{3}+\left(\frac{2}{3}-\frac{3}{4}\right)-\left(0,8+1\frac{1}{5}\right)$

$=\frac{4}{3}+\frac{2}{3}-\frac{3}{4}-0,8-1\frac{1}{5}$

$=\frac{4}{3}+\frac{2}{3}-\frac{3}{4}-\frac{4}{5}-\frac{6}{5}$

$=\left(\frac{4}{3}+\frac{2}{3}\right)-\left(\frac{4}{5}+\frac{6}{5}\right)-\frac{3}{4}$

$=\frac{6}{3}-\frac{10}{5}-\frac{3}{4}=2-2-\frac{3}{4}=\frac{3}{4}$