Построить на канве, график функции y=x^2

unit Unit1;
 
interface
 
uses
  Windows, Messages, SysUtils, Variants, Classes, Graphics, Controls, Forms,
  Dialogs, StdCtrls, ExtCtrls;
 
type
  TForm1 = class(TForm)
    Button1: TButton;
    Image1: TImage;
    procedure Button1Click(Sender: TObject);
  private
    { Private declarations }
  public
    { Public declarations }
  end;
 
var
  Form1: TForm1;
 
implementation
 
{$R *.dfm}
Type TFunc = function (x: real): real;
 
procedure DrawGraph(f: TFunc; a: real; b: real; C: TCanvas);
var x, y, h: real;
    max, min: real;
    sx, sy: real;
    xmid, ymid: integer;
begin
  sx := (c.ClipRect.Right)/(b-a);
  h := 1/sx;
  xmid := c.ClipRect.Right div 2;
  ymid := c.ClipRect.Bottom div 2;
  x := a;
  max := f( x);
  min := max;
  while x<=b do
    begin
      y := f( x);
      if y<min then min := y;
      if y>max then max := y;
      x := x + h;
    end;
  sy := c.ClipRect.Bottom/ (max-min);
  c.Brush.Color := clWhite;
  c.FillRect(Rect(0, 0, c.ClipRect.Right, c.ClipRect.Bottom));
  c.Pen.Color := clBlue;
  c.MoveTo(0, ymid);
  c.LineTo(c.ClipRect.Right, ymid);
  c.MoveTo(xmid, 0);
  c.LineTo(xmid, c.ClipRect.Bottom);
  x := a;
  y := f(x);
  c.Pen.Color := clBlack;
  c.MoveTo(xmid+round(sx*x), ymid-round(sy*y));
  while x<=b do
    begin
      y := f(x);
      c.LineTo(xmid+round(sx*x), ymid-round(sy*y));
      x := x + h;
    end;
end;
 
Function f(x: real): real;
Begin
  Result := x*x;
End;
 
procedure TForm1.Button1Click(Sender: TObject);
begin
  DrawGraph (f, -10, 10, Image1.Canvas);
end;
 
end.