Question

giúp vs

Answer 1

\(\frac{7}{3\times4}-\frac{9}{4\times5}+\frac{11}{5\times6}-\frac{13}{6\times7}+\frac{15}{7\times8}-\frac{17}{8\times9}+\frac{19}{9\times10}\)

\(=\frac{4}{3\times4}+\frac{3}{3\times4}-\frac{5}{4\times5}-\frac{4}{4\times5}+\frac{6}{5\times6}+\frac{5}{5\times6}-\frac{7}{6\times7}-\frac{6}{6\times7}+\frac{8}{7\times8}+\frac{7}{7\times8}-\frac{9}{8\times9}-\frac{8}{8\times9}+\frac{10}{9\times10}+\frac{9}{9\times10}\)

\(=\frac{1}{3}+\frac{1}{4}-\frac{1}{4}-\frac{1}{5}+\frac{1}{5}+\frac{1}{6}-\frac{1}{6}-\frac{1}{7}+\frac{1}{7}+\frac{1}{8}-\frac{1}{8}-\frac{1}{9}+\frac{1}{9}+\frac{1}{10}\)

\(=\frac{1}{3}+\frac{1}{10}=\frac{13}{30}\)