Построение ограниченных областей на плоскости

uses graphaBC;
function f1(x:real):real;
begin
f1:=4*sqr((x+2))
end;
function f2(x:real):real;
begin
f2:=0.5*sqr(x)+4;
end;
function f3(x:real):real;
begin
f3:=4*sqr((x-2))
end;
var xc,yc,i:integer;
    xn,xk,x,mx,my:real;
begin
xc:=windowwidth div 2;
yc:=windowheight-50;
xn:=-1.5;
xk:=1.5;
mx:=(xc-40)/xk;
my:=(yc-40)/f1(0.5);
x:=xn;
moveto(xc+round(x*mx),yc-round(f1(x)*my));
setpencolor(clBlue);
while x<=xk do
 begin
   lineto(xc+round(x*mx),yc-round(f1(x)*my));
  x:=x+0.01
 end;
x:=xn;
moveto(xc+round(x*mx),yc-round(f2(x)*my));
setpencolor(clRed);
while x<=xk do
 begin
   lineto(xc+round(x*mx),yc-round(f2(x)*my));
  x:=x+0.01
 end;
x:=xn;
moveto(xc+round(x*mx),yc-round(f3(x)*my));
setpencolor(clGreen);
while x<=xk do
 begin
   lineto(xc+round(x*mx),yc-round(f3(x)*my));
  x:=x+0.01
 end;
floodfill(xc,yc-100{round(f2(0)*my-10)},clAqua);
setpencolor(clBlack);
line(0,yc,windowwidth,yc);
line(xc,0,xc,windowheight);
setbrushstyle(bsClear);
for i:=1 to 5 do
 begin
  line(xc+round(i*mx/2),yc-3,xc+round(i*mx/2),yc+3);
  textout(xc+round(i*mx/2),yc+10,floattostr(i/2));
  line(xc-round(i*mx/2),yc-3,xc-round(i*mx/2),yc+3);
  textout(xc-round(i*mx/2),yc+10,floattostr(-i/2));
  line(xc-3,yc-round(i*my*5),xc+3,yc-round(i*my*5));
  textout(xc-20,yc-round(i*my*5)-5,inttostr(i*5));
 end;
textout(xc+5,yc+10,'0');
textout(windowwidth-20,yc-20,'X');
textout(xc+10,10,'Y');
setfontsize(12);
setfontcolor(clBlue);
textout(80,10,'y=4(x+2)^2');
setfontcolor(clRed);
textout(80,30,'y=0.5x^2+4');
setfontcolor(clGreen);
textout(80,50,'y=4(x-2)^2');
end.