In which interval will the graph of f(x)=x^3+4x^2-4x-16 be above the x-ais

Question

Please help!!!! A) (-2,2) U (4,infinitiy) B) (-4,-2) U (2, infinity) C) (-infinity, -2) U (-2,9) D) (-4,-2) U (2,4)

Answer 1

Since its a function of the 3rd deegre, it will as x becomes increasingly negative drop. Therefore the values u seek will be found on the positive side. when inserting random positive numbers u will  find that the function becomes positive after x=2, then u can see that the functions limit is approaching the positive infinity.
Answer: ]2,infinity[