Question

[nghiem thi phuong uyen]

\(\frac{4}{3\cdot7}+\frac{5}{7\cdot12}+\frac{1}{12\cdot13}+\frac{7}{13\cdot20}+\frac{8}{20\cdot28}\)

Answer 1

[Trần Thanh Phương]

\(\frac{4}{3\cdot7}+\frac{5}{7.12}+..+\frac{8}{20\cdot28}\)

\(=\frac{1}{3}-\frac{1}{7}+\frac{1}{7}-\frac{1}{12}+...+\frac{1}{20}-\frac{1}{28}\)

\(=\frac{1}{3}-\frac{1}{28}+0+...+0\)

\(=\frac{25}{84}\)

Answer 2

[Nguyễn Tiến Dũng]

\(=\frac{1}{3}-\frac{1}{7}+\frac{1}{7}-\frac{1}{12}+...+\frac{1}{20}-\frac{1}{28}\)

\(=\frac{1}{3}-\frac{1}{28}\)

\(=\frac{25}{84}\)