Question

[Tiểu Ngọc]

1. 1-5/6+7/12-9/20+11/30-13/42+15/56-17/72+19/90

Answer 1

[Ngô Chi Lan]

\(1-\frac{5}{6}+\frac{7}{12}-\frac{9}{20}+\frac{11}{30}-\frac{13}{42}+\frac{15}{56}-\frac{17}{72}+\frac{19}{20}\)

\(=1-\frac{5}{2.3}+\frac{7}{3.4}-\frac{9}{4.5}+\frac{11}{5.6}-\frac{13}{6.7}+\frac{15}{7.8}-\frac{17}{8.9}+\frac{10}{9.10}\)

\(=1-\frac{1}{2}+\frac{1}{10}\)

\(=\frac{3}{5}\)