=a^3 x^4+2abx^2x^2+ab^2-x+b
=a(a^2x^4+2abx^2+b^2)-(x-b)
=a(ax^2+b)^2-(x-b)
=[Va(ax^2+b)+V(x-b)][Va(ax^2+b)-V(x-b)]答案是（ax²-x+b)(a²x²+ax+ab+1)=0