1/1*3+1/3*5+1/5*7+1/7*9+...1/17*19=
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1/1*3+1/3*5+1/5*7+1/7*9+...1/17*19=1/1*3+1/3*5+1/5*7+1/7*9+...1/17*19=1/1*3+1/3*5+1/5*7+1/7*9+...1/1
1/1*3+1/3*5+1/5*7+1/7*9+...1/17*19=
1/1*3+1/3*5+1/5*7+1/7*9+...1/17*19=
1/1*3+1/3*5+1/5*7+1/7*9+...1/17*19=
9/19
=(1-1/3+1/3-1/5+1/5-1/7+...+1/17-1/19)/2
=(1-1/19)/2
=9/19
原式=1/2（1/1-1/3+1/3-1/5+1/5-1/7+1/7-1/9.....+1/17-1/19）=1/2×（1-1/19）=9/19
因1-1/3=2/1*3.则1/1*3=1/2(1-1/3),同理：1/3*5=1/2(1/3-1/5),1/5*7=1/2(1/5-1/7),......1/17*19=1/2(1/17-1/19).所以：原式=1/2(1-1/3+1/3-1/5+1/5-.......-1/19)=1/2*18/19=9/19
1-3+5-7+...
(1+1/3+1/5+1/7)*(1/3+1/5+1/7+1/9)-(1+1/3+1/5+1/7+1/9)*(1/3+1/5+1/7) 简算(1+1/3+1/5+1/7)*(1/3+1/5+1/7+1/9)-(1+1/3+1/5+1/7+1/9)*(1/3+1/5+1/7) 简便计算
1/1*3+1/1*3*5+1/1*3*5*7+1/1*3*5*7*9-73/945
1/3+1/5+1/7+.+1/2n+1
(1/3+1/5+1/7)*(1/5+1/7+1/9)-(1/3+1/5+1/7+1/9)*(1/5+1/7)=?
1 1 1 1 1 3 5 7 1 5 13 25 1 7 25 why
1/1×3+1/3×5+1/5×7+1/7×9.+1/2011×2013
简算:1/1*3+1/3*5+1/5*7+1/7*9+1/9*11
1/1*3+1/3*5+1/5*7+1/7*9+...1/17*19=
计算1/(1×3)+1/(3×5)+1/(5×7)+1/(7×9)+.+1/(19×21)
1/1×3+1/3×5+1/5×7+1/7×9+.+1/2013×2015
1/1*3+1/3*5+1/5*7+1/7*9+.+1/101*103
帮帮忙1/1*3+1/3*5+1/5*7+1/7*9+...1/99*101
1/1*3+1/3*5+1/5*7+1/7*9+1/49*51=
计算：1/1×3+1/3×5+1/5×7+1/7×9``````+1/2001×2003
(1*3)/1+(3*5)/1+(5*7)/1+(7*9)/1+(9*11)/1
1/1*3+1/3*5+1/5*7+1/7*9+1/9*11
(1*3)/1+(3*5)/1+(5*7)/1+(7*9)/1+(9*11)/1