Use interval notation to indicate where is concave up.?

Question

Let f(x)=-x^4-4x^3+2x-2
(A) Use interval notation to indicate where is concave up.
Note: Use 'INF' for , '-INF' for , and use 'U' for the union symbol.
Concave up:

(B) Use interval notation to indicate where is concave down.
Concave down:

(C) List the values of all the inflection points of . If there are no inflection points, enter 'NONE'.
values of inflection points =

Answer 1

Use the second derivative test, not sure exactly what it is still but it should be easy to find on the internet.

Answer 2

#A