Question

Answer 1

\(\dfrac{1}{2.3}+\dfrac{1}{3.4}+\dfrac{1}{4.5}+...+\dfrac{1}{98.99}+\dfrac{1}{99.100}=\dfrac{1}{2}-\dfrac{1}{3}+\dfrac{1}{3}-\dfrac{1}{4}+\dfrac{1}{4}-\dfrac{1}{5}+...+\dfrac{1}{98}-\dfrac{1}{99}+\dfrac{1}{99}-\dfrac{1}{100}=\dfrac{1}{2}-\dfrac{1}{100}=\dfrac{50}{100}-\dfrac{1}{100}=\dfrac{49}{100}\)

Dấu "." là dấu nhân nha

Answer 2

A.\(\dfrac{49}{100}\)

Answer 3

`1/(2xx3) +1(3xx4) +1/(4xx5)+...+1/(98xx99) +1/(99xx100)`

`=1/2 - 1/3 +1/3 -1/4 +1/4 -1/5 +....+1/98 -1/99 + 1/99 -1/100`

`= 1/2 -1/100`

`= 50/100 -100`

`=49/100`

`=> A`