Question

Điền dấu thích hợp :   1/7 + 1/12 + 1/25 + 1/49 + 1/97 ...... 1/3

Answer 1

1/7 + 1/12 + 1/25 + 1/49 + 1/97 < 1/3

 

Answer 2

1/7 + 1/12 + 1/25 + 1/49 + 1/97 < 1/3

Answer 3

Ta có : 1/7 + 1/13 + 1/25 + 1/47 + 1/97 < 1/6 + 1/12 + 1/24 + 1/46 + 1/96

1/7 + 1/13 + 1/25 + 1/47 + 1/97 < 1/6 + 1/6.2 + 1/6.4 + 1/6.8 + 1/6.16

1/7 + 1/13 + 1/25 + 1/47 + 1/97 < 1 + ( 1/2 + 1/4 + 1/8 + 1/16 )

1/7 + 1/13 + 1/25 + 1/47 + 1/97 < 1/6 x ( \(\frac{16+8+4+2+1}{16}\) )

1/7 + 1/13 + 1/25 + 1/47 + 1/97 < 16 x 31/16

1/7 + 1/13 + 1/25 + 1/47 + 1/97 < 31/96 + 31/93

Mà : 91/93 = 1/3

Nên 1/7 + 1/13 + 1/25 + 1/47 + 1/97 < 1/3