How do I write the equation for the plane perpendicular to the xy plane going through y=x?

Basically, I need the equation in the form ax + by + cz + d = 0.


Again, it is the plane perpendicular to the xy plane, and cutting through the xy plane on the line y=x.





This is part of a bigger problem to do with stereographic projection, and I am just kind of having a mental block on how I write the equation for planes! Pretty pathetic considering I'm a math major lol|||If that plane is perpendicular to the xy plane, it is parallel to oz and its equation does not contain z.


So you already have it, think a little