(0.5)^2004+(-0.5)^2005
=(0.5)^2004+(-0.5)(-0.5)^2004
=(0.5)^2004+(-0.5)(0.5)^2004
=(1-0.5)(0.5)^2004
=0.5*(0.5)^2004
=(0.5)^2005
(0.5)^2004+(-0.5)^2005
=(0.5)^2004+(-0.5)(-0.5)^2004
=(0.5)^2004+(-0.5)(0.5)^2004
=(1-0.5)(0.5)^2004
=0.5*(0.5)^2004
=(0.5)^2005