
z axis.
Hi everyone!
So I have to do this problem for homework. However, my book doesn't show us how to draw a graph that involves a zaxis as well as an x and yaxis. It assumes that you know how, and I haven't done this before so I would appreciate any help.

It's hard to say without an example... There are different ways of doing it, or at least to my memory anyway.
Assuming you know what the xy axes look like... now lay it flat on the table, and then draw the an axis coming out of the origin pointing directly out of the table, that's your positive zaxis. If you're still confused, go here: Cartesian coordinate system  Wikipedia, the free encyclopedia
* Get a graphing program that does 3D Graphing... there are free ones on the net.
* Sub in z = 0, see what the xy curve looks like, draw it on the z=0 plane; then repeat with z = 1, z = 2... etc... until you get a feel of what it looks like I guess...
It'd be easier to explain with an equation: $\displaystyle y  x  z = 0$ is the equation of the plane...
z = 0, y  x  0 = 0, this is a line y = x
z = 1, y  x  1 = 0, this is a line y = x + 1
z = 2, y  x  2 = 0, this is a line y = x + 2
By drawing these lines, you'll eventually see that this is a flat plane... which isn't very interesting... there are funky graphs out there.
Perhaps giving us the equation, we might be able to tell you.