1/1X3+1/3X5···+1/33X35
问题描述：
1/1X3+1/3X5···+1/33X35
答
裂项：因为1/n(n+2)=2[1/n-1/(n+2)]
所以 2(1/1-1/3+1/3-1/5+.1/33-1/35)
=2(1-1/35)