How can you tell if a function is quadratic?

There are several ways, but the general format follows f (x) = ax2 + bx + c f (x) = ax² + bx + c, where A, B, and C are non-zero numbers. Another way of finding a quadratic equation is examining the graph of it, you'll notice a "U" shape called a parabola, which come in many shapes but they all retain a "U"-like curve.