由(2008³-2×2008²-2006)/(2008³+2008²-2009)
=[2008²(2008-2)-2006]/[2008²(2008+1)-2009]
=[2006(2008²-1)]/[2009(2008²-1)]
=2006/2009.
由(2008³-2×2008²-2006)/(2008³+2008²-2009)
=[2008²(2008-2)-2006]/[2008²(2008+1)-2009]
=[2006(2008²-1)]/[2009(2008²-1)]
=2006/2009.