Chapter 4 - Applications of the Derivative - 4.2 What Derivatives Tell Us - 4.2 Exercises - Page 256: 5

The graph of f will be above its tangent lines.

Since f'' exists and is positive, the function is concave up. Therefore the tangent lines will be below the graph of f / the graph of f will be above its tangent lines. You can think of it as the tangent lines pushing the graph up.