Let f(x)= -x^4-7x^3+8x+3.

(A) Use interval notation to indicate where https://webwork2.asu.edu/webwork2_fi...910e13a9c1.png is concave up.

Note:Use 'INF' for https://webwork2.asu.edu/webwork2_fi...41e302bd81.png, '-INF' for https://webwork2.asu.edu/webwork2_fi...4d65de8de1.png, and use 'U' for the union symbol.

Concave up:

(B) Use interval notation to indicate where f(x) is concave down.

Concave down:

(C) List the https://webwork2.asu.edu/webwork2_fi...dd0b8b8e91.png values of all the inflection points of https://webwork2.asu.edu/webwork2_fi...faee426371.png. If there are no inflection points, enter 'NONE'.

https://webwork2.asu.edu/webwork2_fi...dd0b8b8e91.png values of inflection points =