Tính giá trị biểu thức: P= 1/1.2 + 1/2.3 +1/3.4 +......+1/99.100

$\Longrightarrow$P `=` $\dfrac{1}{1·2}$ `+` $\dfrac{1}{2·3}$ `+...+` $\dfrac{1}{99·100}$

    `=` `1` `-` $\dfrac{1}{2}$ `+` $\dfrac{1}{2}$ `-` $\dfrac{1}{3}$ `+...+` $\dfrac{1}{99}$ - $\dfrac{1}{100}$

    `=` `1` `-` $\dfrac{1}{100}$

    `=` $\dfrac{99}{100}$

`@Jong`