\(\frac{2}{5\cdot7}+\frac{2}{7\cdot9}+\frac{2}{9\cdot11}+\frac{2}{11\cdot13}+\frac{2}{13\cdot15}\)
\(=\frac{1}{5}-\frac{1}{7}+\frac{1}{7}-\frac{1}{9}+\frac{1}{9}-\frac{1}{11}+....-\frac{1}{15}\)
\(=\frac{1}{5}-\frac{1}{15}=\frac{2}{15}\)
Các câu hỏi tương tự
28 tháng 12 2021 lúc 9:50
\(\frac{2}{5x7}\)+\(\frac{2}{7x9}\)+\(\frac{2}{9x11}\)+\(\frac{2}{11x13}\)+\(\frac{2}{13x15}\)=
tính nhanh
\(\frac{2}{3x5}+\frac{2}{5x7}+\frac{2}{7x9}+\frac{2}{9x11}+\frac{2}{11x13}+\frac{2}{13x15}+\frac{2}{1x2}+\frac{2}{2x3}+\frac{2}{3x4}+...+\frac{2}{8x9}+\frac{2}{9x10}\)
giải hẳn ra cho mình ai làm đúng mình tk cho nhé !!!
\(\frac{2}{5x7}+\frac{2}{7x9}+\frac{2}{9x11}+...+\frac{2}{13x15}\)
Tính nhanh tổng sau:
\(\frac{2}{1x3}\)+ \(\frac{2}{3x5}\)+ \(\frac{2}{5x7}\)+ \(\frac{2}{7x9}\)+ \(\frac{2}{9x11}\)+ \(\frac{2}{11x13}\)
Ai lam dung va nhanh nhat, minh tick cho!
Tìm y biết:
\(\left(\frac{2}{1x3}+\frac{2}{3x5}+\frac{2}{5x7}+\frac{2}{7x9}+\frac{2}{9x11}\right)\cdot y=\frac{2}{3}\)
Tính nhanh 2/3x5+2/5x7+2/7x9+2/9x11+2/11x13+2/13x15 +2/1x2+2/2x3+2/3x4+.........+2/8x9+2/9x10
Tính Nhanh
a) \(\frac{1995x1997-1}{1996x1995+199}\) b) \(\frac{2}{3x5}\) + \(\frac{2}{5x7}\) + \(\frac{2}{7x9}\) + \(\frac{2}{9x11}\) + ..... + \(\frac{2}{13x15}\)
Tính bằng cách thuận tiện:
\(\frac{3}{5x3}\)+ \(\frac{3}{5x7}\)+\(\frac{3}{7x9}\)+\(\frac{3}{9x11}\)+\(\frac{3}{11x13}\)
#(các bạn giúp mik nha, mk sẽ tích đúng)
\(\left(\frac{1}{1x3}+\frac{1}{3x5}+\frac{1}{5x7}+\frac{1}{7x9}+\frac{1}{9x11}\right)\)