LeoStatistic software for data presentation, statistical analysis, marketing and prediction. Free download: 
View function.
The best way to understand behavior of a unknown function. LeoStatistic makes this task a quite trivial. Here is step by step an example how to prepare a function to view. Open LeoStatistic. In tab "Data" click on "Insert" button. , Select name "x", and "Insert as Argument" and leave all other parameters as they are. Click "Insert". It will create 1000 records of argument array from 0 to 9.99. Click again on "Insert" button in "Data" tab . Select name "y", add as "Value" check "From formula", print in edit control "2.5*(abs(x4.9)abs(x5.1))+0.5". Click "Insert" Repeat previous step without any change except printing other formulas:
Result screenshot of LeoStatistic will looks like this: Not literally exact because we refuses from "Autozoom" option and set custom y minimum range. Special case is presenting a so named parametric functions when both argument and value are functions of other parameter. To show such function on LeoStatistic follow to the same procedure as described before and create following parameters:
Result has to be as shown below: Parametric functions could be considered also as projection of curve in space on one of the coordinates plane. More about fitting such kind if curves you could read here. 
Screenshots of the LeoStatistic software: click on picture to enlarge
