Построить график функций: y=3x*x  — Pascal(Паскаль)

program graf;
{y=x^3+2*x^2+x}
uses graph;
var
   centerx,centery,gx,gy:integer;
   x,y,sx,sy:real;
 
procedure open_graph;
var
   graph_device,graph_mode:integer;
begin
   graph_device:=Detect;
   InitGraph(graph_device, graph_mode, ' ');
   if GraphResult <> grOk then
   begin
      writeln('Oshibka');
      readln;
      halt;
   end;
end;
 
procedure close_graph;
begin
   CloseGraph;
   if GraphResult <> grOk then
   begin
      writeln('Oshibka');
      readln;
      halt;
   end;
end;