ai trả lời ko?? nếu ko thì mik trả lời nè!!!
a) \(x-10\left(\frac{2}{15.17}+\frac{2}{17.19}+...+\frac{2}{73.75}\right)=\frac{7}{15}\)
\(x-10\left(\frac{1}{15}-\frac{1}{17}+\frac{1}{17}-\frac{1}{19}+...+\frac{1}{73}-\frac{1}{75}\right)=\frac{7}{15}\)
\(x-10\left(\frac{1}{15}-\frac{1}{75}\right)=\frac{7}{15}=>x-\frac{8}{15}=\frac{7}{15}=>x=1\)
b) \(x-10\left(\frac{2}{11.13}+\frac{2}{13.15}+...+\frac{2}{53.55}\right)=\frac{3}{11}\)
\(x-10\left(\frac{1}{11}-\frac{1}{55}\right)=\frac{3}{11}=>x-\frac{8}{11}=\frac{3}{11}=>x=1\)