This is a short plug for mathworksheetsgo.com free online graphing calculator which is a great tool for exploring graphs of various functions.
You start with this form.
And you get a graph like this.
This has only scratched the surface of what this tool can do.
Go here matworksheetsgo.com free online graphing calculator and have a play. If you have children them let them have a play too.
When I were a lad we had to do all this with graph paper and pencils!