Question

1,Tính nhanh

a,3x\(\left(\frac{1}{7}+\frac{1}{3}-\frac{3}{14}\right):\frac{11}{14}\)

b,\(\left(\frac{21}{8}+\frac{1}{2}\right):\frac{5}{6}\)

3,Tìm x,biết

a,\(\frac{1}{3}+\frac{1}{6}+\frac{1}{10}+......+\frac{2}{x\cdot\left(x+1\right)}=\frac{2016}{2018}\)

b,720:\(720:[41-\left(2\cdot x-5\right)]=120\)

Answer 1

Câu b:

\(\frac{21}{8}:\frac{5}{6}+\frac{1}{2}:\frac{5}{6}\)

= \(\frac{63}{20}+\frac{3}{5}\)

= \(\frac{15}{4}\)

Answer 2

\(\left(\frac{21}{8}+\frac{1}{2}\right):\frac{5}{6}\)

\(\frac{25}{8}:\frac{5}{6}\)

\(\frac{25}{8}.\frac{6}{5}\)

\(\frac{30}{8}\)