Question

\(Chứngtỏrằng:\frac{1}{^22}+\frac{1}{^23}+\frac{1}{^24}+\frac{1}{^25}+\frac{1}{^26}+\frac{1}{^27}+\frac{1}{^28}< 1\)

chứng tỏ rằng 1 phần 2 mũ 2+1 phần ba mũ 2...........

Answer 1

giải luôn; đặt A=1/2^2+1/3^2+...+1/8^2

1/2^2 < 1/1.2

1/3^2<1/2.3

.......

1/8^2<1/7.8

=> 1/2^2 + 1/3^2 +...+1/8^2<1/1.2  + 1/2.3 + ....+ 1/7.8

=>A<1-1/2 + 1/2 - 1/3 + ....+1/7-1/8

=>A<1-1/8<1 

vậy 1/2^2+1/3^2+....+1/8^2 <1 

like nha