原式=（x^4+2x^3-3x^2)-4(x+3)
=x^2(x^2+2x-3)-4(x+3)
=x^2(x+3)(x-1)-4(x+3)
=(x+3)[x^2(x-1)-4)
=(x+3)(x^3-x^2-4)
x^4+2x^3-3x^2-4x-12因式分解,急用
原式=（x^4+2x^3-3x^2)-4(x+3)
=x^2(x^2+2x-3)-4(x+3)
=x^2(x+3)(x-1)-4(x+3)
=(x+3)[x^2(x-1)-4)
=(x+3)(x^3-x^2-4)