de dung nhu the nay
1/1x2+1/2x3+1/3x4+...+1/2010x2011
= 1/1-1/2+1/2-1/3+1/3-1/4+...+1/2010-1/2011
=1/1-1/2011
=2010/2011
\(1-\frac{1}{2}+\frac{1}{2}-\frac{1}{3}+\frac{1}{3}-\frac{1}{4}+.....+\frac{1}{2010}-\frac{1}{2011}.\)
\(1-\frac{1}{2011}=\frac{2010}{2011}\)
xong gồi đó
=\(\frac{1}{1}\)\(-\)\(\frac{1}{2}\)\(+\)\(\frac{1}{2}\)\(-\)............\(+\)\(\frac{1}{2010}\)\(-\)\(\frac{1}{2011}\)
=\(1\)\(-\frac{1}{2011}\)
\(=\frac{2010}{2011}\)
1/1-1/2+1/2-1/3+1/3-1/4+1/4-.............+1/2010-1/2011
= 1-1/2011
=2010/2011
Nhớ tk cho mình nhé
