Question

\(\frac{3}{5x7}+\frac{3}{7x9}+...+\frac{3}{59x61}\)

giup minh nhe

Answer 1

\(\frac{3}{5x7}+\frac{3}{7x9}+...+\frac{3}{59x61}\)

\(=\frac{3}{2}\left(\frac{2}{5x7}+\frac{2}{7x9}+...+\frac{2}{59x61}\right)\)

\(=\frac{3}{2}.\left(\frac{1}{5}-\frac{1}{7}+\frac{1}{7}-\frac{1}{9}++...+\frac{1}{59}-\frac{1}{61}\right)\)

\(=\frac{3}{2}\left(\frac{1}{5}-\frac{1}{61}\right)\)

\(=\frac{3}{2}.\frac{56}{305}=\frac{84}{305}\)

Answer 2

Nguyễn Tuấn Minh giải đúng rồi nhé