Ошибка в программе с графиком и функцией

Program grafik;
uses crt,graphabc;
var gd,gm,errCode:integer; a,b:real; n:integer;
function f(x:real):real;
 begin if x<>0 then f:=ln(x+1)-exp(2*(x-2)); end;
procedure grafin (x0,x1,y0,y1,n:word; a,b:real);
var h,m,x,t1,t2:real; i,u,v,xv,yv:word;
begin
h:=(b-a)/n; m:=abs(f(a));
for i:=1 to n do if m<abs (f(a+i*h)) then m:=abs(f(a+i*h));
t1:=(x1-x0)/(b-a); t2:=(y1-y0)/(2*m);
xv:=round(x0-a*t1); yv:=round((y0+y1)/2);
setcolor(1); line(xv,y0,xv,y1);
line (x0,yv,x1,yv);
moveto (x0,yv-round(f(a)*t2));
setcolor(3);
for i:=1 to n do
 begin
 x:=a+i*h;
 u:=x0+round((x-a)*t1);
 v:=yv-round(f(x)*t2);
 linetvo(u,v);
 end;
end;
begin
clrscr; write ('введ a b n:'); readln (a,b,n); gd:=detect;
initGraph (gd,gm, '');
errCode:=GraphResult;
if errCode=grOk then
 begin grafin (100,500,50,300,n,a,b);
 grafin (550,620,10,100,200,-0.1,0.1);
 repeat until keypressed; CloseGraph;
 end
 else writeln('errCode=',errCode);
 End.

Program grafik;
uses crt,graphabc;
var a,b:real;
    n:integer;
function f(x:real):real;
begin
f:=ln(x+1)-exp(2*(x-2));
end;
procedure grafin (x0,x1,y0,y1,n:word; a,b:real);
var h,m,x,t1,t2:real;
    i,u,v,xv,yv:integer;
begin
h:=(b-a)/n;
m:=abs(f(a));
for i:=1 to n do
if m<abs (f(a+i*h)) then m:=abs(f(a+i*h));
t1:=(x1-x0)/(b-a);
t2:=(y1-y0)/(2*m);
xv:=round(x0-a*t1); yv:=round((y0+y1)/2);
setpencolor(clBlue);
line(xv,y0,xv,y1);
line (x0,yv,x1,yv);
moveto (x0,yv-round(f(a)*t2));
setpencolor(clGreen);
for i:=1 to n do
 begin
  x:=a+i*h;
  u:=x0+round((x-a)*t1);
  v:=yv-round(f(x)*t2);
  lineto(u,v);
 end;
end;
begin
write ('введ a b n:');
read (a,b,n);
hidecursor;
clearwindow;
grafin (100,500,50,300,n,a,b);
grafin (550,620,10,100,200,-0.1,0.1);
End.