Question

[Girl Xinh]

1. Làm giúp mk câu 11.

Answer 1

[Chó Doppy]

\(\frac{1}{1x2}\)+\(\frac{1}{2x3}\)+...+\(\frac{1}{2010X2011}\)
=1-\(\frac{1}{2}\)+\(\frac{1}{2}\)-\(\frac{1}{3}\)+...+\(\frac{1}{1010}\)-\(\frac{1}{2011}\)
=1-\(\frac{1}{2011}\)
=\(\frac{2010}{2011}\)

Answer 2

[Ridofu Sarah John]

1. \(\frac{1}{1x2}+\frac{1}{2x3}+\frac{1}{3x4}+..+\frac{1}{2010x2011}\\\frac{1}{1}-\frac{1}{2}+\frac{1}{2}-\frac{1}{3}+\frac{1}{3}-\frac{1}{4}+..+\frac{1}{2010}-\frac{1}{2011}\\ \frac{1}{1}-\frac{1}{2011}\)