Question

[Nguyễn Lâm Tuấn]

\(\dfrac{6}{2.5}+\dfrac{2}{5.7}+\dfrac{6}{8.11}+...+\dfrac{6}{59.62}+\dfrac{6}{62.65}\)

giúp mình từng bước một nhé

Answer 1

[Nguyễn Lê Phước Thịnh]

Sửa đề: \(\dfrac{6}{2\cdot5}+\dfrac{6}{5\cdot8}+...+\dfrac{6}{62\cdot65}\)

\(=2\left(\dfrac{3}{2\cdot5}+\dfrac{3}{5\cdot8}+...+\dfrac{3}{62\cdot65}\right)\)

=3(1/2-1/5+1/5-1/8+...+1/62-1/65)

=3*63/130=189/130