(a+2)(a2+4)(a-2)-(a2+8)(a2-2)=(a2+4)(a2-4)-(a2+8)(a2-2)=(a^4-16)-(a^4+6a2-16)=-6a2
(a+2)(a+4)(a-2)-(a+8)(a-2)=(a+2)(a-2)(a+4)-(a+8)(a-2)=(a-4)(a+4)-(a+8)(a-2)=a^4-16-(a^4+6a-16)=a^4-16-a^4-6a+16=-6a
