graph5

import geometry;
import graph;
import contour;

size(9cm, 0);
defaultpen(fontsize(12pt));
dotfactor = 4;
picture axis;

real xmin = -5, xmax = 5,
     ymin = -5, ymax = 5;
xaxis(axis, xmin=xmin, xmax=xmax,
    Ticks(scale(.7)*Label(align=E, Fill(white) ),
          NoZero,
          beginlabel=false, endlabel=false,
          begin=false, end=false,
          Step=0, step=0,
          Size=0mm, size = 0mm),
          Arrow(2mm),true);

yaxis(axis, ymin=ymin, ymax=ymax,
    // Ticks(scale(.7)*Label(align=W, Fill(white) ),
    //      NoZero,
    //      beginlabel=false, endlabel=false,
    //      begin=false, end=false,
    //      Step=0, step=0,
    //      Size=0mm, size = 0mm),
          Arrow(2mm),true);

real f(real x,real y){
  return (x^2+2*x)*y-2;
}
guide[][] Cf = contour(f,(xmin,ymin),(xmax,ymax),nx=400,ny=400, new real[]{0}, operator ..);
draw(Cf[0], green+1pt);

label("$x$", (xmax,0), 2S);
label("$y$", (0,ymax), 2W);
//label(scale(.7)*"$0$", origin, S+W, UnFill);
ylimits(ymin, ymax, Crop);
add(axis);
addMargins(2mm,2mm);