Very well. See http://cs.gettysburg.edu/~tneller/resources/k12/index.html for a tutorial that demonstrates the use of the 'turtle' built in module in python. Turtle has a long history of being a simple graphical environment to introduce programming to young individuals, and that hasn't changed over the years. It would meet the original post author's requirements for graphing those simple functions.

Assuming you are targeting those -slightly- older, pyglet would offer an incredibly simple way to progress, but would require you download one library, which I feel is a very reasonable requirement.