2007/2008x2009
=2007/2008x(2008+1)
=2007/2008 x2008+2007/2008
=2007又2007/2008
2009分之2008*2008
=2008/2009x2008
=2008/2009x(2009-1)
=2008/2009x2009-2008/2009
=2008-2008/2009
=2007又1/2009
思路是把整数部分拆成含有负数中父母的形式,可以和父母约分,再用乘法分配律.
不懂得继续问哦^_^