Coi A=1/1x3+1/3x5+1/5x7+1/7x9
=>2A=2x(1/1x3+1/3x5+1/5x7+1/7x9)=2/1x3+2/3x5+2/5x7+2/7x9
=1-1/3+1/3-1/5+1/5-1/7+1/7-1/9
=1-1/9=8/9
=>A=8/9:2=4/9
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1/1x3 + 1/3x5 + 1/5x7 + 1/7x9
1/1x3+1/3x5+1/5x7+1/7x9
1/1x3+1/3x5+1/5x7+1/7x9=1/9x11
1/1x3+1/3x5+1/5x7+1/7x9+1/9x11 = ?
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 )
(1/1x3+1/3x5+1/5x7+1/7x9+1/9x11+1/11x13)xy=3/5
tìm y:(1/1x3+1/3x5+1/5x7+1/7x9+1/9x11)xy=2/3
a,1/1x3+1/3x5+1/5x7+1/7x9+1/X=1;b,2/3-1/3x(X-2)=1/4
\(\left(\frac{1}{1x3}+\frac{1}{3x5}+\frac{1}{5x7}+\frac{1}{7x9}+\frac{1}{9x11}\right)\)