The problem comes when the icon that it defaults to for printing is a right load, but the only way that envelopes can be loaded is in the center of the tray. I have an HP Colorlaserjet 3600 and an HP Officejet Pro 8600 and both load this way.
A technical definition of a function is: a relation from a set of inputs to a set of possible outputs where each input is related to exactly one output.
Below are some examples of these types of functions: y = 2x + 1 y = 3x2 - 5x + 3 y = Sin(x) x2 + y2 = 4 y2 = x3 - Tan(x). These algebraic functions are all different and have different properties. It is often useful to have a visual way to look at these functions. Graphs provide such a tool.