We then add 1 onto this, but again, this will yield a single value. So, when there is something other than the variable inside the parenthesis we are really asking what the value of the function is for that particular quantity.
However, evaluation works in exactly the same way. In other words, we just need to make sure that the variables match up.
Recall the mathematical definition of absolute value. Circles are never functions. If you keep that in mind you may find that dealing with function notation becomes a little easier. From the equation, you can determine the missing variable. Be careful. Here are the evaluations. Recall, that from the previous section this is the equation of a circle.
In other words, we only plug in real numbers and we only want real numbers back out as answers.