Tính các tổng sau: a) 1/2 + -2/3 + 1/6 + 3/7 b) 1/2 + 2/3 + 3/4 + 4/5 + 5/6

* Hướng dẫn giải

a) $\frac{1}{2}+\frac{-2}{3}+\frac{1}{6}+\frac{3}{7}=\frac{3}{6}+\frac{-4}{6}+\frac{1}{6}+\frac{3}{7}=\frac{3}{7}$

b) $\frac{1}{2}+\frac{2}{8}+\frac{3}{4}+\frac{4}{5}+\frac{5}{6}$$=\frac{30}{60}+\frac{40}{60}+\frac{45}{60}+\frac{48}{60}+\frac{50}{60}=\frac{71}{5}$