(x+2)(x-2)(x²+4)(x⁴+16)
=(x²-4)(x²+4)(x⁴+16)
=(x⁴-16)(x⁴+16)
=x^8-16^2
=x^8-256
20042005²-20042004²
=2004(2005²-2004²)
=2004(2005+2004)(2005-2004)
=2004*2009
=4026036