\(A=\frac{1}{2.3}+\frac{1}{3.4}+...+\frac{1}{99.100}\)

ta có: \(\frac{1}{2.3}=\frac{1}{2}-\frac{1}{3}\)

\(\frac{1}{3.4}=\frac{1}{3}-\frac{1}{4}\)

...

\(\frac{1}{99.100}=\frac{1}{99}-\frac{1}{100}\)

Vậy \(A=\frac{1}{2.3}+\frac{1}{3.4}+...+\frac{1}{99.100}\)

\(=\frac{1}{2}-\frac{1}{3}+\frac{1}{3}-\frac{1}{4}+\frac{1}{4}-\frac{1}{5}+...+\frac{1}{99}-\frac{1}{100}\)

\(=\frac{1}{2}-\frac{1}{100}\)

\(=\frac{50}{100}-\frac{1}{100}=\frac{49}{100}\)

vậy A = 49/100

\(A=\dfrac{1}{2}-\dfrac{1}{3}+\dfrac{1}{3}-\dfrac{1}{4}+...+\dfrac{1}{99}-\dfrac{1}{100}=\dfrac{1}{2}-\dfrac{1}{100}=\dfrac{49}{100}\)

\(A=\dfrac{1}{2.3}+\dfrac{1}{3.4}+...+\dfrac{1}{99.100}\)

\(=\dfrac{1}{2}-\dfrac{1}{3}+\dfrac{1}{3}-\dfrac{1}{4}+...+\dfrac{1}{99}-\dfrac{1}{100}=\dfrac{1}{2}-\dfrac{1}{100}=\dfrac{49}{100}\)

`A=1/(2.3) + 1/(3.4) +........ +1/(99.100)`

`=1/2-1/3+1/3-1/4+......+1/99-1/100`

`=1/2-1/100`

`=49/100`

nhanh lên 

A=1/1-1/2+1/2-1/3+1/3-1/4+...............+1/99-1/100

A=1/1-1/100

A=100/100-1/100

A=99/100

Mk ko chép đề bài

\(A=\frac{1}{1}-\frac{1}{2}+\frac{1}{2}-\frac{1}{3}.+.....+\frac{1}{99}-\frac{1}{100}\)

\(A=1-\frac{1}{100}\)

\(A==\frac{99}{100}\)

kết quả = 99/100 tick mik đúng nhé

Ai tích cho toi thi h lai cho

Ta có: 1/2-1/3+1/3-1/4+1/4-1/5+...+1/99-1/100
         = 1/2-1/100
         = 50/100-1/100
         = 49/100

A = 1/2 - 1/3 + 1/3 -1/4 + 1/4 -1/5 + ...+ 1/98 - 1/99 + 1/99 - 1/100 
Ta thấy đoạn giữa sẽ bị trừ lẫn nhau nên bằng 0 
A = 1/2 - 1/100 = 49/100

tích nha

A=1-1/2+1/2-1/3+1/3-1/4+.........+1/99-1/100

A=1-1/100

A=99/100

ai k mk      mk k lai 

A=1-1/100

A=99/100

Nha bạn       

A = 1 - 1/2 + 1/2 - 1/3 + ......+ 1/99 - 1/100

A =  1 - 1/100

A = 99/100

Ai k mk mk k lại !

\(=1-\dfrac{1}{2}+\dfrac{1}{2}-\dfrac{1}{3}+\dfrac{1}{3}-\dfrac{1}{4}+...+\dfrac{1}{99}-\dfrac{1}{100}\\ =1-\dfrac{1}{100}=\dfrac{99}{100}\)

=1/1-1/2+1/2-1/3+1/3-1/4+....+1/99-1/100

=1-1/100

=99/100

=1−1/2+1/2−1/3+1/3−1/4+...+1/99−1/100
=1 − 1/100 = 99/100

1/1.2 + 1/2.3 + 1/3.4 + ... + 1/99.100

= 1 - 1/2 + 1/2 - 1/3 + 1/3 - 1/4 + ... + 1/99 - 1/100

= 1 - 1/100

= 99/100