Question

[Pham Tien Dat]

Cho: A = \(\frac{1}{101}+\frac{1}{102}+....+\frac{1}{200}\). CMR : A > \(\frac{7}{12}\)

Answer 1

[Trần Thị Loan]

\(A=\left(\frac{1}{101}+\frac{1}{102}+...+\frac{1}{150}\right)+\left(\frac{1}{151}+\frac{1}{152}+...+\frac{1}{200}\right)\)

Nhận xét:

\(\frac{1}{101}+\frac{1}{102}+...+\frac{1}{150}>\frac{1}{150}+\frac{1}{150}+...+\frac{1}{150}=\frac{1}{150}.50=\frac{1}{3}\)

\(\frac{1}{151}+\frac{1}{152}+...+\frac{1}{200}>\frac{1}{200}+\frac{1}{200}+...+\frac{1}{200}=\frac{1}{200}.50=\frac{1}{4}\)

=> A> 1/3 + 1/4 = 7/12 => đpcm

Answer 2

[nhok buồn vui]

ƠI GIÚP MK CÂU NHƯ THẾ NHƯNG  CMRA>5/8

BN NHA