Question

[Vũ Đức Thành]

1/6 + 1/12 + 1/20 - 1/35 bằng bao nhiêu

giúp mik vs

Answer 1

[Nguyễn Lê Phước Thịnh]

\(\dfrac{1}{6}+\dfrac{1}{12}+\dfrac{1}{20}-\dfrac{1}{35}\)

\(=\dfrac{1}{2\cdot3}+\dfrac{1}{3\cdot4}+\dfrac{1}{4\cdot5}-\dfrac{1}{35}\)

\(=\dfrac{1}{2}-\dfrac{1}{3}+\dfrac{1}{3}-\dfrac{1}{4}+\dfrac{1}{4}-\dfrac{1}{5}-\dfrac{1}{35}\)

\(=\dfrac{1}{2}-\dfrac{1}{5}-\dfrac{1}{35}=\dfrac{3}{10}-\dfrac{1}{35}=\dfrac{3\cdot7-2}{70}=\dfrac{19}{70}\)