(2008/2009)x2008=(2008/2009)x(2009-1)(=2008/2009)x2009-2008/2009=2008-2008/2009=2007又1/2009
2009分之2008×2008
=2009分之2008×(2009-1)
=2009分之2008×2009-2009分之2008×1
=2008-2009分之2008
=2007又2009分之1
2008×2008/2009
=2008²/2009
=(2008²-1+1)/2009
=[(2008+1)(2008-1)+1]/2009
=(2009×2007+1)/2009
=2007+1/2009
2008/2009*2008=(1-1/2009)*2008=2008-2008/2009=2007又1/2009
2008/2009×2008
=2008/2009×(2009-1)
=2008-2008/2009
=2007又1/2009