(1/2+1/3+。。。+1/2011)(1+1/2+1+1/3+....+1/2010)-(1+1/2+....+1/2011)(1/2+1/3+....1/2010)
=(1/2+1/3+。。。+1/2011)(1/2+1+1/3+....+1/2010)-(1/2+....+1/2011)(1/2+1/3+....1/2010)
+(1/2+1/3+。。。+1/2011)-(1/2+1/3+....1/2010)
=(1/2+1/3+。。。+1/2011)-(1/2+1/3+....1/2010)
=1/2011
设A=1/2+1/3+。。。+1/2011 B=1/2+1+1/3+....+1/2010
原式
=A*(1+B)-(1+A)*B
=A+AB-B-AB
=A-B
=(1/2+1/3+。。。+1/2011)-(1/2+1+1/3+....+1/2010)
=1/2011
记A=(1/2+1/3+。。。+1/2011)
B=(1+1/2+1+1/3+....+1/2010)
原式即求AB-(1+A)(B-1)=AB-(B-A-1+AB)=A-B+1=1/2011
原式
=(1/2+1/3+。。。+1/2011))(1/2+1+1/3+....+1/2010)-(1/2+....+1/2011)(1/2+1/3+....1/2010)
+(1/2+1/3+。。。+1/2011)-(1/2+1/3+....1/2010)
=1/2011