①﹙a+1﹚²﹙a-1﹚²
=[(a+1)(a-1)]²
=(a²-1)²
=a^4-2a²+1
②2009²-2008×2010
=2009²-(2009-1)×(2009+1)
=2009²-(2009²-1)
=2009²-2009²+1
=1