Question

Tính 1/1.2+1/2.3+1/3.4+......+1/2005.2006 (tổng này có 2005 số hạng)

Answer 1

1/1.2 + 1/2.3 + 1/3.4 + ... + 1/2005.2006

= 1/1 - 1/2 + 1/2 - 1/3 + 1/3 - 1/4 + ... + 1/2005 - 1/2006

= 1/1 - 1/2006

= 2005/2006

cho mình 1 đ-ú-n-g nha bạn

Answer 2

\(\frac{1}{1\cdot2}+\frac{1}{2\cdot3}+\frac{1}{3\cdot4}+...+\)\(\frac{1}{2005\cdot2006}\)

\(=\frac{1}{1}-\frac{1}{2}+\frac{1}{2}-\frac{1}{3}+\frac{1}{3}-\frac{1}{4}+...+\frac{1}{2005}-\frac{1}{2006}\)

\(=\frac{1}{1}-\frac{1}{2006}\)

\(=\frac{2006}{2006}-\frac{1}{2006}\)

\(=\frac{2005}{2006}\)