原式=[(a-b)^2+(a+b)^2][(a-b)^2-(a+b)^2]
=(a^2-2ab+b^2+a^2+2ab+b^2)[(a-b-a-b)(a-b+a+b)]
=2(a^2+b)^2[-2b*2a]
=-8ab(a^2+b^2)
