explain with an example

A polynomial function is a function defined by evaluating a polynomial. A function ƒ of one argument is called a polynomial function if it satisfies.

Above polynomial is said to be:

1.Linear-When n=1. An example is f(x)=x+3            2.Quadratic-When n=2. AN example is f(x)=x²+9x+81 3.Cubic- When n=3. For example 7x³+9x²+10x+12