2007×2008.2008-2008×2007.2007
=2007×(2008+0.2008)-2008×(2007+0.2007)=2007×0.2008-2008×0.2007
=2007×(0.2007+0.0001)-(2007+1)×0.2007
=2007×0.0001-0.2007
=0
2007×2008.2008-2008×2007.2007
=2007×(2008+0.2008)-2008×(2007+0.2007)=2007×0.2008-2008×0.2007
=2007×(0.2007+0.0001)-(2007+1)×0.2007
=2007×0.0001-0.2007
=0