Đáp án : A =$\dfrac{49}{100}$
Giải thích A = $\dfrac{1}{2.3}$ + $\dfrac{1}{3.4}$ + ...+ $\dfrac{1}{98.99}$ + $\dfrac{1}{99.100}$
A = $\dfrac{1}{2}$ - $\dfrac{1}{3}$ + $\dfrac{1}{3}$ - $\dfrac{1}{4}$ + ...+ $\dfrac{1}{98}$- $\dfrac{1}{99}$ + $\dfrac{1}{99}$ - $\dfrac{1}{100}$
A = $\dfrac{1}{2}$ - $\dfrac{1}{100}$
A = $\dfrac{50}{100}$ - $\dfrac{1}{100}$ = $\dfrac{49}{100}$
Vậy A = $\dfrac{49}{100}$
