A function and its graph are given. Use the second derivative to determine each of the following. Check your results against the graph shown. f( x ) = _x* 1x4 + 1x3 - 3x2 + 4 f(x) 20 15 10 51 X -8 -6 -4 2 4 6 8 -10 - 15 -20 Determine intervals on which the function is concave up. (Enter your answer using interval notation.) Determine intervals on which the function is concave down. (Enter your answer using interval notation.) Locate the points of inflection. (If an answer does not exist, enter DNE.) (x, y ) = (smaller x-value) ( x, y) = (larger x-value)