Question

[Đinh Thành Long]

c/m A=1/2(1/6+1/24+1/60+...........+1/9240)>57/462 làm chi tiết mình tick cho

Answer 1

[maivantruong]

A=\(\frac{1}{2}.\left(\frac{1}{6}+\frac{1}{24}+\frac{1}{60}+.......+\frac{1}{9240}\right)>\frac{57}{462}\)ta nhóm 6 là ngoài

A=\(\frac{1}{2}.6.\left(1+\frac{1}{4}+\frac{1}{10}+.........+\frac{1}{9240}\right)>\frac{57}{462}\)

A=3.(1+\(\frac{1}{1540}\))

A=3.\(\frac{1541}{1540}\)

A=3 

\(\Rightarrow\)3>\(\frac{1541}{1540}\)

Answer 2

[maivantruong]

quen 

3>\(\frac{57}{462}\)