A function is a relation between a set of inputs and a set of possible outputs where each input is related to exactly one output. The domain is the set of all possible input values, while the range is the set of all possible output values. In this example, we have the function f of x equals x squared. When we input negative 2, the function gives us exactly one output, which is 4.
Function notation uses the form f of x, where f is the name of the function, x is the input variable, and f of x represents the output value. For example, if we define a function f of x equals 2x plus 3, then when we input 1, the function gives us f of 1 equals 5. Similarly, when we input 2, we get f of 2 equals 7. This linear function can be visualized as a straight line on the coordinate plane.