(2x^-5x-4)(3x^-7x+8)=6x^4-14x^3+16x^2-15x^3+35x^2-40x-12x^2+28x-32=6x^4-29x^3+39x^2-12x-32
(2x^-5x-4)(3x^-7x+8)用多项式*多项式=6x^4-29x^3+39x^2-12x-32