\(\frac{5}{5.7}+\frac{5}{7.9}+...+\frac{5}{59.61}\)
\(=\frac{5}{2}\left(\frac{2}{5.7}+\frac{2}{7.9}+...+\frac{2}{59.61}\right)\)
\(=\frac{5}{2}\left(\frac{1}{5}-\frac{1}{7}+\frac{1}{7}-\frac{1}{9}+...+\frac{1}{59}-\frac{1}{61}\right)\)
\(=\frac{5}{2}\left(\frac{1}{5}-\frac{1}{61}\right)=\frac{5}{2}.\frac{56}{305}=\frac{28}{61}\)
\(\frac{3}{5\cdot7}+\frac{3}{7\cdot9}+........+\frac{3}{59\cdot61}\)
giải chi tiết giúp mình nha mình cần gấp lắm mình cảm ơn nhìu
\(\frac{4}{5\cdot7}+\frac{4}{7\cdot9}+\frac{4}{9\cdot11}+...+\frac{4}{59\cdot61}\)
\(\frac{3}{5\cdot7}\)+ \(\frac{3}{7\cdot9}\) + ......+\(\frac{3}{59\cdot61}\)
S=\(\frac{1}{2}\) + \(\frac{1}{2^2}\) +......+\(\frac{1}{2^{20}}\)
Tính tổng
A=\(\frac{2}{3\cdot5}+\frac{2}{5\cdot7}+\frac{2}{7\cdot9}+...+\frac{2}{97\cdot99}\)
Tính M
\(M=\frac{1}{5\cdot7}+\frac{1}{7\cdot9}+\frac{1}{9\cdot11}+...+\frac{1}{101\cdot103}\)
tính nhanh
\(\frac{6^2}{5\cdot7}\cdot\frac{7^2}{6\cdot8}\cdot\frac{8^2}{7\cdot9}\cdot\frac{9^2}{8\cdot10}\)
\(1\frac{1}{3\cdot5}+\frac{4}{5\cdot7}+\frac{1}{7\cdot9}+...+\frac{1}{99\cdot101}\)
95*.Tính nhanh
\(\frac{2}{3\cdot5}+\frac{2}{5\cdot7}+\frac{2}{7\cdot9}+...+\frac{2}{97\cdot99}\)
Tính \(21\cdot\left(\frac{4}{1\cdot3}-\frac{8}{3\cdot5}+\frac{12}{5\cdot7}-\frac{16}{7\cdot9}+...+\frac{36}{17\cdot19}-\frac{40}{19\cdot21}\right)\)
