1又2006分之1X2005又2007分之1 =2007/2006x［(2005x2007)+1］/2007 =［(2005x2007)+1］/2006 =2005x2007/2006+1/2006 =2005x(2006+1)/2006+1/2006 =2005+1/2006+1/2006 =2005+2/2006 =2005又1003分之1