One factor of $x^3+x^2-4x-4$ is $(x+1)$. The remaining two factors are:

Group the terms in pairs: $x^2(x+1)-4(x+1)=(x+1)(x^2-4)$. The bracket is a difference of squares, so $x^2-4=(x-2)(x+2)$. (Reading $x^2-4$ as a perfect square gives the repeated factor $(x+2)(x+2)$, which would expand to $x^2+4x+4$.) Expanding $(x+1)(x-2)(x+2)$ returns $x^3+x^2-4x-4$.