Thanks for the field plot, but I really need the phase portrait, and I couldn't figure out how to use it from the help thing in maple.

Thank you very much, that worked great!

Thanks a lot for your help, but now I'm getting an error after the last statement: > plots[display](P1, P2) Error, (in plots:-display) expecting plot structure but received: DEplot(diff(y(x), x) = 2*x+2*(x^2-y(x))^(1/2), y(x), x = -2 .. 2, y = -2 .. 2, colour = red)