Question

D = 1/ 10 + 1/15 + 1/20 + ... 1/ 120

Ai nhanh nhất mk tick cho

Answer 1

Đề bài sai rồi nha bn, p/s thứ 3 fai là 1/21 ms đúng

D = 1/10 + 1/15 + 1/21 + ... + 1/120

D = 2 × (1/20 + 1/30 + 1/42 + ... + 1/240)

D = 2 × (1/4×5 + 1/5×6 + 1/6×7 + .... + 1/15×16)

D = 2 × (1/4 - 1/5 + 1/5 - 1/6 + 1/6 - 1/7 + ... + 1/15 - 1/16)

D = 2 × (1/4 - 1/16)

D = 2 × (4/16 - 1/16)

D = 2 × 3/16

D = 3/8

Answer 2

D=1/10+1/15+1/20+..+1/120

=>D=0,5551916356

=> D=0,5551916356

Answer 3

D=1/5*2+1/5*3+1/5*4+...+1/5*24

D=1/5-1/2+1/5-1/3+1/5-1/4+...+1/5-1/24

D=1/5-1/24

D=19/120

vậy 1/10+1/15+1/20+...+1/120=19/120