2x^4+x^3+7x^2+4x-4
=2x^4+x^3-x^2+8x^2+4x-4
=x^2(2x^2+x-1)+4(2x^2+x-1)
=(x^2+4)(2x^2+x-1)
=(x^2+4)(2x-1)(x+1)