Question

\(\frac{1}{1}x\frac{1}{2}+\frac{1}{2}x\frac{1}{3}+...+\frac{1}{6}x\frac{1}{7}+\frac{1}{7}x\frac{1}{8}\)

giải hộ mik nha

nhanh nhanh nhé mik cần lắm

 

Answer 1

\(=\frac{1}{1\cdot2}+\frac{1}{2\cdot3}+...+\frac{1}{7\cdot8}\)

\(=\frac{1}{1}-\frac{1}{2}+\frac{1}{2}-\frac{1}{3}+\frac{1}{3}-...-\frac{1}{8}\)

\(=\frac{1}{1}-\frac{1}{8}=\frac{7}{8}\)

Answer 2

\(=\frac{1}{1.2}+\frac{1}{2.3}+...+\frac{1}{3.7}+\frac{1}{7.8}\)

\(=1-\frac{1}{2}+\frac{1}{2}-\frac{1}{3}+...+\frac{1}{7}-\frac{1}{8}\)

\(=1-\frac{1}{8}+0+0+...+0\)

\(=\frac{7}{8}\)

Answer 3

= \(\frac{1}{1.2}+\frac{1}{2.3}+...+\frac{1}{6.7}+\frac{1}{7.8}\)
= \(\frac{1}{1}-\frac{1}{2}+\frac{1}{2}-\frac{1}{3}+...+\frac{1}{6}-\frac{1}{7}+\frac{1}{7}-\frac{1}{8}\)
= \(1-\frac{1}{8}=\frac{7}{8}\)

Answer 4

Ta có : 1/1 . 1/2 + 1/2.1/3 + .....+ 1/7.1/8

= 1 - 1/2 + 1/2 - 1/3 + .....+ 1/7 - 1/8

= 1 - 1/8

= 7/8

Answer 5

thanks các bạn nhìu nha!!!^-^