Question

Tính T=1/2+5/6+11/12+...+89/90+109/110+10/11

Answer 1

Tớ sửa chút, phải bằng 10

Answer 2

  1/2 + 5/6 + 11/12 + ... + 89/90 + 109/110 + 10/11

= (1 - 1/2) + (1 - 1/6) + (1 - 1/12) + ... + (1 - 1/90) + (1 - 1/110) + 10/11

= (1 + 1 + 1 + 1 + 1 + 1 + 1 + 1 + 1) - (1/1*2 + 1/2*3 + 1/3*4 + ... + 1/10*11) + 10/11

= 9 - (1 - 1/11) + 10/11

= 9 - 10/11 + 10/11 = 9

Answer 3

T=1/2+5/6+11/12+...+89/90+109/110+10/11

T= (1 -1/2) + ( 1 - 1/6) + (1-1/12) + (1-1/20)+(1-1/30)+... + (1 - 1/90) + (1- 1/110) + 10/11

T= 1x10 –(1/2+1/6+1/12+1/20+……..+1/90+1/110)+10/11

T=10 – (1-1/2+1/2-1/3+1/3-1/4+1/4-1/5+……+1/9-1/10+1/10-1/11)+ 10/11

T= 10 – (1-1/11)+10/11 = 10-10/11+10/11

T=10