(1/1x3)+(1/3x5)+(1/5x7)+……+(1/49x51)=

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(1/1x3)+(1/3x5)+(1/5x7)+……+(1/49x51)=
如题

设数列An通项=1/[(2n-1)(2n+1)] n≥1且n∈Z
An= 1/[(2n-1)(2n+1)]= 1/2* [1/(2n-1) -1/(2n+1)]
记数列An的前n项和为Sn.
则：Sn=1/2[1-1/(2n+1)],（累加相消）
∴ Sn=(1/1x3)+(1/3x5)+(1/5x7)+……+(1/49x51)=1/2[1-1/(2*25+1)]=25/51

1+2x3+4x5+6x7+.50x51的和是奇数还是偶数?写出原因 1/1x3+1/3x5+1/5x7+……+1/99x101 1/1x3+1/3x5+1/5x7+…+1/2011x2013是多少? 1X3分之一+3X5分之一+5X7分之一…+2011X2013分之一 1/1X3+1/3X5+1/5X7...1/17X19+1/19X21= 1/1x3+1/3x5+1/5x7+1/7x9+1/9x11=? 1/1x3+1/3x5+1/5x7+.+1/2009x2011= 2/1x3+2/3X5+2/5x7=2/7x9+2/9x11 计算：1/1x3+1/3x5+1/5x7+1/7x9+……+1/2011x2013 1/1x3+1/3x5+1/5x7.1/2009x2010+1/2011x2013 计算：1/1x3+1/3x5+1/5x7+...1/2009x2011+1/2011×2013 1/(1x3)+1/(3x5)+1/(5x7)+.+1/(2011x2013) 等于什么