Given the graph of the function f below, determine all intervals where f(x) is concave up on the open interval (-9,9). Drag the yellow point to see the graph of f'
plotted in real time.

“exterior angles of triangles. an exterior (or external) angle is the angle between one side of a triangle and the extension of an adjacent side. try this drag the orange dots on any vertex to reshape the triangle.” look to get to the answer i explained what it means and other things i hope it you .

The answer would be c