Bài tập 1. Bỏ dấu ngoặc rồi tính.

a) $(\frac{−3}{8})+(\frac{7}{9}−\frac{5}{8})$

b) $\frac{4}{9}−(\frac{3}{7}+\frac{2}{9})$

c) $[(\frac{−2}{5})+\frac{1}{3}]−(\frac{3}{5}−\frac{1}{4})$

d) $(1\frac{1}{2}−\frac{3}{4})−(0.25+\frac{1}{2})$

Hướng dẫn trả lời. 

a) $(\frac{−3}{8})+(\frac{7}{9}−\frac{5}{8})= (\frac{−3}{8})+\frac{7}{9}−\frac{5}{8}=(\frac{−3}{8})+(\frac{−5}{8})+\frac{7}{9}=−1+\frac{7}{9}=\frac{−2}{9}$

b) $\frac{4}{9}−(\frac{3}{7}+\frac{2}{9})=\frac{4}{9}−\frac{3}{7}-\frac{2}{9})= \frac{4}{9}−\frac{2}{9}−\frac{3}{7}=\frac{2}{9}−\frac{3}{7}=\frac{−13}{63}$

c) $[(\frac{−2}{5})+\frac{1}{3}]−(\frac{3}{5}−\frac{1}{4})= (\frac{−2}{5})+\frac{1}{3}−\frac{3}{5}+\frac{1}{4}= (\frac{−2}{5})+(\frac{−3}{5})+\frac{1}{3}+\frac{1}{4}=−1+\frac{7}{12}=\frac{−5}{12}$

d) $(1\frac{1}{2}−\frac{3}{4})−(0.25+\frac{1}{2})=\frac{3}{2}−\frac{3}{4}−\frac{1}{4}−\frac{1}{2}=\frac{3}{2}−\frac{1}{2}−\frac{3}{4}−\frac{1}{4}$=0