ax^2+2xy+x^2-x--bxy+y=(a+1)x^2+(2-b)xy-x-y
∵x,y的多项式ax^2+2xy+x^2-x--bxy+y不含二次项
∴a+1=0 2-b=0
∴a=-1 b=2
∴-ab^3+2a^3b+3ab^3-4a^3b=8-4-24+8=-12