Find intervals on which the graph of

y = x⁴ 4x³ 18x² + 6

is concave up and intervals on which it is concave down. (Enter your answers using interval notation. If an answer does not exist, enter DNE.)

concave up?

concave down?

Find the points of inflection. (Order your answers from smallest to largest x, then from smallest to largest y. If an answer does not exist, enter DNE.)

smaller x-value

larger x-value