Answer:
Let y = f(x) be a function with an independent variable x and a dependent variable y.
If a function f provides a way to successfully produce a single value y using for that purpose a value for x then that
chosen x-value is said to belong to the domain of f. If there is a requirement that a y-value produced by a function
must be a real number, the following conditions are commonly checked:
1. Denominators cannot equal 0.
2. Radicands (expressions under a radical symbol) of even roots (square roots, etc)
cannot have a negative value.
3. Logarithms can only be taken of positive values.
4. In word problems physical or other real-life restrictions might be imposed, e.g. time is
nonnegative, number of items is a nonnegative integer, etc.
