I don't understand how to determine the domain of concave up versus concave down when the graph has two points of inflection.
x^4 + 8x^3 + 18x^2 + 8
extreme points: -3, 0
(graph is high at -3 and low at 0)
Points of inflection: -3, -1
My textbook says the answer is
concave up (- infinity , -3) , ( -1, inifinity)
Concave down ( -3 , -1)