2 NG CHEP MANG

WHAT LA CAI GI 
TRA LOI:WHAT LA CAI GI

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

Mik lam giong pan Huynh Chau Giang nhe

Nhan vao day nhe

SAY You Do hay day

ro rang de bai ra chu ban?