Ta có: \(\frac{2}{3\times5}+\frac{2}{5\times7}+\cdots+\frac{2}{49\times51}\)
\(=\frac13-\frac15+\frac15-\frac17+\cdots+\frac{1}{49}-\frac{1}{51}\)
\(=\frac13-\frac{1}{51}=\frac{17}{51}-\frac{1}{51}=\frac{16}{51}\)
1x3/3x5 + 2x4/5x7 + 3x5/7x9 + ............... +49x51/99x101
1x3/3x5 + 2x3/5x7 + 3x5/7x9 + ............... +49x51/99x101
2/1x3 + 2/3x5 + 2/5x7 + 2/7x9 + 2/9x11
2/3x5 + 2/5x7 + 2/7x9 + 2/9x11 + 2/11x13
a, 2/1x3 + 2/3x5 + 2/5x7 + 2/7x9 +...+ 9/913 x 215
b,1/1x3 + 1/3x5 + 1/5x7 + 1/7x9 + 1/213 x 215
[ Giúp mik với mấy bạn ơi ai nhanh mình sẽ tick nha TvT ]
( Toán tính nhanh nha )
Tính nhanh
2/1x3 + 2/3x5 + 2/5x7 + 2/7x9 +...+ 2/19x21
3/3x5 + 2/5x7 + 2/7x9 +2/113x115
giúp mình nha
Tính biểu thức sau
2/3x5+2/5x7+2/7x9+.....................+2/21x23+2/23x25
\(\frac{2}{3x5}+\frac{2}{5x7}+\frac{2}{7x9}+...+\frac{2}{17x19}\)
