Question

[Trương Minh Phương]

so sánh A vơi 1. Biết  \(A=\frac{5}{5x6}+\frac{5}{6x7}+\frac{5}{7x8}+\frac{5}{8x9}+\frac{5}{9x10}+\frac{5}{10x11}\)

Mong các bạn giúp giùm thank

Answer 1

[Trương Nguyễn Tú Anh]

A= 5.(1/5.6+1/6.7+...+1/10.11)

A=5.(1/5-1/6+1/6-1/7+.....+1/10-1/11)

A=5.(1/5-1/11)

A=5.6/55=6/11

Answer 2

[Trương Nguyễn Tú Anh]

A=6/11<1

A<1