Question

[Ngân Nguyễn]

\(\left(\frac{2}{11.13}+\frac{2}{13.15}+..............\frac{2}{19.21}\right).462-\frac{17}{x+1.05}=19\)

Tìm x

Answer 1

[Nguyễn Xuân Anh]

\(\Leftrightarrow\left(\frac{1}{11}-\frac{1}{13}+\frac{1}{13}-\frac{1}{15}+...+\frac{1}{19}-\frac{1}{21}\right).462-\frac{17}{x+1,05}=19.\)

\(\Leftrightarrow\left(\frac{1}{11}-\frac{1}{21}\right)462-\frac{17}{x+1,05}=19\)

\(\Leftrightarrow20-\frac{17}{x+1,05}=19\)

\(\Leftrightarrow1-\frac{17}{x+1,05}=0\)

\(\Leftrightarrow x+1,05=17\)

\(\Leftrightarrow x=15,95\)