Question

\(G=\frac{1}{2x9}+\frac{1}{9x7}+\frac{1}{7x19}+.....+\frac{1}{252x509}\)

Tính G 

Answer 1

\(G=\frac{1}{2.9}+\frac{1}{9.7}+\frac{1}{7.19}+...+\frac{1}{252.509}\)

\(G=2.\left(\frac{1}{4.9}+\frac{1}{9.14}+\frac{1}{14.19}+...+\frac{1}{504.509}\right)\)

\(G=\frac{2}{5}.\left(\frac{5}{4.9}+\frac{5}{9.14}+\frac{5}{14.19}+...+\frac{5}{504.509}\right)\)

\(G=\frac{2}{5}.\left(\frac{1}{4}-\frac{1}{9}+\frac{1}{9}-\frac{1}{14}+\frac{1}{14}-\frac{1}{19}+...+\frac{1}{504}-\frac{1}{509}\right)\)

\(G=\frac{2}{5}.\left(\frac{1}{4}-\frac{1}{509}\right)\)

\(G=\frac{2}{5}.\frac{505}{2036}=\frac{101}{1018}\)

Answer 2

Khó quá !!!

Answer 3

khó thiệt

Answer 4

khó quá