填空 1/1006
设那个空为X,等式两边同时乘以2011x2012,得出X=4022/2011x2012,（4022=2011x2）,所以X=1/1006
同理,1/n +1/(n+1)-x=n*(n+1),得出X=2/(n+1),然后带进去.
稍微掉一下位置,(1/2+1/12-1/6)-(1/7+1/8-1/56)-(1/9-1/90-1/30)=1/10,这是不按规律算.
下面按规律算(由N的规律算)
1/6=1/2+1/3-1/3
1/12=1/3+1/4-1/2
1/56=1/7+1/8-1/4
1/90=1/10+1/9-1/5
1/30=1/5+1/6-1/3
1/2=1/1+1/2-1
所以1/2-(1/2+1/3-1/3)+(1/3+1/4-1/2)-1/7+(1/5+1/6-1/3)-1/8+(1/7+1/8-1/4)-1/9+(1/10+1/9-1/5)=1/10