Помогите с паскалем (

Procedure grafic(xmin,xmax:real);

Var
dp, dy, ymin, ymax: real;
i, q,Tg,tv,dn,dk,dg,dv:integer;
x, y:word;
f, r:real;

Begin
clrscr;
textout(280,20,'y=(x^3+2x^2-15)/2');
SetPenColor(clBlack);
for i:=1 to 28 do
line(30+i*20,50,30+20*i,350);
for i:=1 to 16 do
line(50,30+20*i,590,30+20*i);

ymin := (Xmin*Xmin*Xmin+2*Xmin*Xmin-15)/2 ;
ymax := (Xmax*Xmax*Xmax+2*Xmax*Xmax-15)/2 ;

dp:=(540/(Xmax-Xmin));
dy:=(300/(ymax-ymin));
Tg:= 50 - round(xmin*dp);
tv:= 50 + round(ymax*dy);
SetPenColor(clRed);
line(tg,45,tg,355);
line(40,tv,600,tv);

r := xmin;
x := trunc(tg + dp*xmax) ;
f := (xmin*xmin*xmin+2*xmin*xmin-15)/2 ;
y := trunc(tv - dy*f) ;
putpixel(x,y,0);

while (r