Question

[khanh duy]

chung to rang B= 1/2^2+1/3^2+1/4^2+1/5^2+1/6^2+1/7^2+1/8^2<1

Answer 1

[soyeon_Tiểu bàng giải]

B = 1/2² + 1/3² + 1/4² + 1/5² + 1/6² + 1/7² + 1/8² < 1/1.2 + 1/2.3 + 1/3.4 + 1/4.5 + 1/5.6 + 1/6.7 + 1/7.8

B =                                                                   < 1 - 1/2 + 1/2 - 1/3 + 1/3 - 1/4 + 1/4 - 1/5 + 1/5 - 1/6 + 1/6 - 1/7 + 1/7 - 1/8

B =                                                                   < 1 - 1/8 < 1

=> đpcm