Question

chứng minh rằng

C = 1/101 + 1/102 + 1/103 + ... + 1/200 > 7/12

Answer 1

Ta có 

1/101 > 1/150

1/102> 1/150

...>1/150

1/150 = 1/150

=> 1/101 + 1/102 + .... + 1/150 > 1/150 +1/150+....+1/150(50 số hạng )= 1/3

Answer 2

ta thấy 

1/101>1/150

1/102>1/150

...

1/150=1/150

=> 1/101+1/102+...+1/150>1/150+....+1/150(50 sô hạng)

=>1/101+1/102+...+1/150>1/3

1/151>1/200+

1/152>1/200

....

1/200=1/200

=>1/151+1/152+...+1/200>1/200+...+1/200(50 sô hạng)

=> 1/151+1/152+...+1/200>1/4

=> 1/101+...+1/200>1/3+1/4=7/12