2/3=1/2+1/6 2/5=1/3+1/15 2/7=1/4+1/28 2/9=1/5+1/45

一般结论是：2/(2n-1)=1/n+1/n(2n-1);(n>=2)说明计算下就好了1/n+1/n(2n-1)=[(2n-1)+1]/n*(2n-1)=2/(2n-1);验证n=2;2/(2n-1)=2/31/n+1/n(2n-1)=1/2+1/2*3=1/2+1/6;n=32/(2n-1)=2/51/n+1/n(2n-1)=1/3+1/3*5=1/3+1/15....