mình làm kiểu này không biết có đúng không nữa
đặt A =3/5x7+3/7x9+3/9x11+....................+3/63x65
Ax2=2/5x7+2/7x9+2/9x11+........................+2/63x65
Ax2=3/5-3/7+3/7-3/9+3/9+3/11+.....................+3/63-3/65
Ax2=3/5-3/65
A=36/65:2
A=18/65
Tìm y biết:
\(\left(\frac{2}{1x3}+\frac{2}{3x5}+\frac{2}{5x7}+\frac{2}{7x9}+\frac{2}{9x11}\right)\cdot y=\frac{2}{3}\)
\(\frac{2}{5x7}+\frac{2}{7x9}+\frac{2}{9x11}+...+\frac{2}{13x15}\)
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)
\(\left(\frac{1}{1x3}+\frac{1}{3x5}+\frac{1}{5x7}+\frac{1}{7x9}+\frac{1}{9x11}\right)\)
Tính
\(\frac{1}{1x3}+\frac{1}{3x5}+\frac{1}{5x7}+\frac{1}{7x9}+\frac{1}{9x11}\)
1, Tìm x
\(\frac{1}{5x7}+\frac{1}{7x9}+\frac{1}{9x11}+.....+\frac{1}{2009x2011}+\frac{1}{x}=\frac{1}{5}x0,5\)
\(\hept{\begin{cases}\\\end{cases}}\frac{1}{1x3}\)+\(\frac{1}{3x5}\) + \(\frac{1}{5x7}\)+ \(\frac{1}{7x9}\)+ \(\frac{1}{9x11}\)} x Y = \(\frac{2}{3}\)
Tìm Y
\(\frac{3}{5x7}+\frac{3}{7x9}+...+\frac{3}{59x61}\)
giup minh nhe
\(\frac{2}{5x7}\)+\(\frac{2}{7x9}\)+\(\frac{2}{9x11}\)+\(\frac{2}{11x13}\)+\(\frac{2}{13x15}\)=
