Question

chứng minh rằng : 1/25+1/26+1/27+...+1/54 <39/40

Answer 1

<1/25+1/25+...+1/25+1/40+1/40+1/40+...+1/40

=1/25.15+1/40.15=15/25+15/40=3/5+3/8=39/40

Answer 2

đặt vế trái là A ta có A<1/25.16+1/45.14=214/225=1-11/225 39/40=1-1/40 ta có 1.225<11.40=>1/40<11/225=>1-1/40>1-11/225=>214/225<39/40 mà A<214/225=>A<39/40(đpcm nhớ k cho mk nha

Answer 3

=1/25+1/54

=79/1350

vi 79/1350<39/40

nen 1/25+1/26+1/27+...1/54<39/40

Answer 4

 cx,mnm,cnslkd