Question

\(\left(\frac{2}{11.13}+\frac{2}{13.15}+.........\frac{2}{19.20}\right)-x+\frac{221}{231}=\frac{4}{3}\)

Answer 1

\(\left(\frac{2}{11.13}+\frac{2}{13.15}+...+\frac{2}{19.20}\right)-x+\frac{221}{231}=\frac{4}{3}\)

\(=\left(\frac{1}{11}-\frac{1}{13}+\frac{1}{13}-\frac{1}{15}+...+\frac{1}{19}-\frac{1}{20}\right)-x=\frac{4}{3}-\frac{221}{231}\)

\(=\left(\frac{1}{11}-\frac{1}{20}\right)-x=\frac{29}{77}\)

\(=\frac{9}{220}-x=\frac{29}{77}\)

\(x=\frac{9}{220}-\frac{29}{77}\)

 

Answer 2

bạn ơi chỗ \(\frac{2}{19.20}\) có phải là \(\frac{2}{19.21}\) không