Rather than have a graph of 2 variables sometimes it is beneficial to have a third variable, generally .
In order to easily work within 3d space vectors and matrices are often used.
Within 3-Dimensional space there are functions, , and lines , but we now also have planes. Rather than only having one input to each output you can now have many different inputs to one output.
If we fed the above equation the output would be , but the last variable doesn't matter as it's not in the equation, so if we looked at a graph of this line it wouldn't be a line but instead a plane (or surface):
See the following for info about different equations and their respective graphs:
