Tớ sửa chút, phải bằng 10

  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

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

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

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

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

= 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

= 10 – (1 - 1/11) + 10/11

= 10 - 10/11 + 10/11

= 10

\(A=\left(1-\frac{1}{2}\right)+\left(1-\frac{1}{6}\right)+\left(1-\frac{1}{12}\right)+....+\left(1-\frac{1}{90}\right)+\left(1-\frac{1}{110}\right)+\frac{10}{11}\)

\(=10-\left(\frac{1}{1.2}+\frac{1}{2.3}+\frac{1}{3.4}+....+\frac{1}{10.11}\right)+\frac{10}{11}=10-\left(1-\frac{1}{11}\right)+\frac{10}{11}=10\)

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

nếu muốn hỏi 1x10 ở đâu thì vì 1x10 là lấy từ 10 con số 1 trong mỗi số hạng của

(1 -1/2) + ( 1 - 1/6) + (1-1/12) + (1-1/20)+(1-1/30)+... + (1 - 1/90) + (1- 1/110)

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

 Nếu muốn hỏi 1x10 ở đâu thì vì 1x10 là lấy từ 10 con số 1 trong mỗi số hạng của

(1 -1/2) + ( 1 - 1/6) + (1-1/12) + (1-1/20)+(1-1/30)+... + (1 - 1/90) + (1- 1/110).

quá đúng cô giáo mình cũng làm như vậy

1/2=1-1/2

5/6=1-1/6

11/12=1-1/12

109/110=1-1/110

A=10-(1/2+1/6+...+1/110)

B=(1/2+1/6+...+1/110)=[(1-1/2)+(1/2-1/3)+(1/3-1/4)+...+(1/9-1/10)+(1/10+1/11)

B=1+1/11

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