After I ran the following I got a valid image but what do the r's stand for in the solve part? They don't seem to have a value but I didn't get an error.
var('x y') show(plot3d(x^2 + y^2, (x,-2,2), (y,-2,2))) [image]
solve(x^2 + y^2==0,[x,y]) [[x == r1, y == Ir1], [x == r2, y == -Ir2]]