Tính: \(\Large{A=10\times(\dfrac{1}{2}+\dfrac{1}{6}+\dfrac{1}{12}+\dfr

Tính:

$\Large{A=10\times(\dfrac{1}{2}+\dfrac{1}{6}+\dfrac{1}{12}+\dfrac{1}{20})}$

• A. Đáp án: 8

$\Large{A=10\times(\dfrac{1}{2}+\dfrac{1}{6}+\dfrac{1}{12}+\dfrac{1}{20})}$

= $\Large{A=10\times(\dfrac{1}{1\times2}+\dfrac{1}{2\times3}+\dfrac{1}{3\times4}+\dfrac{1}{4\times5})}$

= $\Large{A=10\times(\dfrac{1}{1} - \dfrac{1}{5})}$

= $\Large{A=10\times\dfrac{4}{5}}$

= 8

Đáp số: 8