Functions and graphs

Equations of a straight line of the form y = mx + c, for example y = 2x + 4 are also functions. This example can be written as f(x) = 2x + 4. This can be plotted as y = f(x).

The same is true of quadratic equations of the form y = ax^2 + bx + c, for example y = x^2 + 2x - 3. This example can be written as f(x) = x^2 + 2x - 3. This can also be plotted as y = f(x)