x(4次方)-2x(3次方)-7x(2次方)+ 8x+12=x^4+x^3-3x^3-3x^2-4x^2-4x+12x+12=(x^4+x^3)+(-3x^3-3x^2)+(-4x^2-4x)+(12x+12)=x^3(x+1)-3x^2(x+1)-4x(x+1)+12(x+1)=(x+1)(x^3-3x^2-4x+12)=(x+1)[(x^3-3x^2)+(-4x+12)]=(x+1...