Question

1)1/4+1/12+1/24+1/40+1/60+1/84

2)tìm x

1/2011x=(1-1/2)(1-1/3)(1-1/4)......(1-1/2010)(1-1/2011)

Answer 1

\(\frac{1}{4}+\frac{1}{12}+\frac{1}{24}+\frac{1}{40}+\frac{1}{60}+\frac{1}{84} \)
\(=\frac{210}{840}+\frac{70}{840}+\frac{35}{840}+\frac{21}{840}+\frac{14}{840}+\frac{10}{840}\)
\(=\frac{210+70+35+21+14+10}{840}\)
\(=\frac{360}{840}\)
\(=\frac{3}{7}\)