graphing equations

[Doug Wyble]

Hi I'm a high school teacher and want to learn how to use octave to do help 
students visualize math. we a currently working on linear programming 
problems. i'm having a hard time plotting planes in 3-D. I want to be able 
to plot three planes on the same graph. for example 
2x+y+z=4  x+y+z=2  3x-y-z=2 so students can see the point of intersection. 
Is there anyway you could help me get started with this. Also is there a 
good manual anywhere to learn octave. If i got a MATLAB manual would that 
be helpful THANKS
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