TI-83 Plus calculator problem?

I have been using TI-83 calculators for a while and never saw anything like that. I would say check the window and adjust the max and min. Its possible that something is wrong with the calculator or that it is just what the equation looks like when graphing, but I highly doubt that because most of the time when graphing an equation there is almost always some type of line. Try just putting numbers in instead of equations and see if that works. If not, contact them about it or find someone that is really good with calculators.