This is looking at how the CURVE of the graph opens–concave up (positive parabola) or concave down (negative parabola). Definition: If a function’s graph is BELOW all of its tangent line, concave down. If a function’s graph is ABOVE all of its tangent line, concave up– hence why we use the 2nd derivative to determine … Continue reading 4.4- Concavity and the Second Derivative Test