解答：(1)(-x)^8-[(-3x)^4]^2+8[-(-x)^4]^2=x^8-81x^8+8x^8=-72x^8(2)2(-xy)^9*y^3=-2x^9y^12(3)[4(x-y)]^2=16(x-y)^2(4)(-a^(n+1))^2*(-a^3)^(2n-1)=a^(2n+2)*(-1)*a^(3n-3)=-a^(5n-1)
