What is the domain?

The domain of a function is the complete set of possible values of the independent variable; the set of all possible x values which will make the function 'work', and output real y values.

When finding the domain, it is important to remember that the denominator of a fraction cannot be zero, and the number under a square root sign must be positive.

To determine the domain of a function f(x), we must identify the values of x for which the function f(x) returns real values. Sketching or using a graph-drawing tool can thus help to identify the domain of functions.