Question

` B=1/6+1/12+1/20+1/30+1/42+1/56+1/72+1/90 `

Answer 1

Câu trả lời chi tiết :

\(B = \dfrac{1}{6}+\dfrac{1}{12}+\dfrac{1}{20}+\dfrac{1}{30}+\dfrac{1}{42}+\dfrac{1}{56}+\dfrac{1}{72}+\dfrac{1}{90} \)

\(B = \dfrac{1}{2.3}+\dfrac{1}{3.4}+\dfrac{1}{4.5}+\dfrac{1}{5.6}+\dfrac{1}{6.7}+\dfrac{1}{7.8}+\dfrac{1}{8.9}+\dfrac{1}{9.10}\)

\(B = \dfrac{1}{2}-\dfrac{1}{3}+\dfrac{1}{3}-\dfrac{1}{4}+......+\dfrac{1}{9} - \dfrac{1}{10}\)

\(B = \dfrac{1}{2}-\dfrac{1}{10}\)

\(B = \dfrac{5}{10}-\dfrac{1}{10}\)

\(B = \dfrac{4}{10}\)

\(B = \dfrac{2}{5}\)