2008*(2008/2009)
=(2009+1-2)*[(2009-1)/2009]
=(2009+1)*[(2009-1)/2009]-2*[(2009-1)/2009]
=(2009*2009-1)/2009-[(2009*2-1*2)/2009]
=2009-1/2009-2+2/2009
=2007+1/2009
2007又1/2009
2008*(2008/2009)
=(2009+1-2)*[(2009-1)/2009]
=(2009+1)*[(2009-1)/2009]-2*[(2009-1)/2009]
=(2009*2009-1)/2009-[(2009*2-1*2)/2009]
=2009-1/2009-2+2/2009
=2007+1/2009
2007又1/2009