Построить графики функций и найти точки их пересечения

 uses
  GraphAbc;
 
label 1;
 
var
  a, b, c, x, y, nn, n: integer;
  x1, y1: real;
  bol: byte;
 
procedure table;
begin
  Line(WindowWidth div 2, 40, WindowWidth div 2, 700);
  Line(250, WindowHeight div 2, 1025, WindowHeight div 2);
  for nn := 0 to 370 do
  begin
    if nn mod 10 = 0 then begin
      Line(WindowWidth div 2 + nn + 10, WindowHeight div 2, WindowWidth div 2 + nn + 10, WindowHeight div 2 + 4);
      Line(WindowWidth div 2 - nn - 10, WindowHeight div 2, WindowWidth div 2 - nn - 10, WindowHeight div 2 + 4);
      Line(WindowWidth div 2, WindowHeight div 2 + nn + 10, WindowWidth div 2 + 4, WindowHeight div 2 + nn + 10);
      Line(WindowWidth div 2, WindowHeight div 2 - nn - 10, WindowWidth div 2 + 4, WindowHeight div 2 - nn - 10);
 
    end; end;
end;
 
begin
  MaximizeWindow; table;
  writeln('êàêàÿ ôóíêöèÿ?');
  writeln('1=>êâàäðàòíàÿ');
  writeln('2=>ëèíåéíàÿ');
  readln(bol);
1:
  if bol = 1 then begin
    write('a='); read(a); writeln(a);
    write('b='); read(b); writeln(b);
    write('c='); read(c); writeln(c);
 
    x := -b div a; x := x div 2;
    y := (a * x * x) + (b * x) + c;
    moveto(WindowWidth div 2 + (x * 10), WindowHeight div 2 - (y * 10));
 
    for x := 0 to 30 do
    begin
      y := (a * x * x) + (b * x) + c;
      lineto(WindowWidth div 2 + (x * 10), WindowHeight div 2 - (y * 10));
    end;
    x := -30;
    for n := 0 to 30 do
    begin
      x :=x+1;
      y := (a * x * x) + (b * x) + c;
      lineto(WindowWidth div 2 + (x * 10), WindowHeight div 2 - (y * 10));
    end;
  end;
 
  if bol = 2 then begin
    write('a='); read(a); writeln(a);
    write('b='); read(b); writeln(b);
    moveto(WindowWidth div 2, WindowHeight div 2);
    for x := -30 to 30 do
    begin
      y := (a * x) + b;
      lineto(WindowWidth div 2 + (x * 10), WindowHeight div 2 - (y * 10));
    end;
  end;
 
writeln('Êàêàÿ ôóíêöèÿ äàëüøå?');   //Ââåäè íîëü äëÿ âûõîäà
read(bol);
if bol<>0 then goto 1;
 
end.

uses graphABC;
function F1(x:real):real;
begin
F1:=x*x*x*x;
end;
function F2(x:real):real;
begin
F2:=2*x-16;
end;
var xn,xk,x,mx,my,dx,x1:real;
    x0,y0,n,i:integer;
    s,s1,s2:string;
begin
xn:=-3;//èíòåðâàë ïî Õ
xk:=3;
x0:=windowwidth div 2;//íà÷àëî êîîðäèíàò
y0:=windowheight-100;
mx:=(x0-10)/xk;//ìàñøòàá ïî Õ
my:=(y0-40)/F1(xk);//ìàñøòàá ïî Y
line(0,y0,windowwidth,y0);//îñè
line(x0,0,x0,windowheight);
for i:=1 to trunc(F1(xk))+1 do//ðàçáèâêà îñåé êîîðäèíàò
  begin
    line(x0+round(i*mx),y0-3,x0+round(i*mx),y0+3); //çàñå÷êè íà îñè Õ
    line(x0-round(i*mx),y0-3,x0-round(i*mx),y0+3);
    line(x0-3,y0+round(i*my*10),x0+3,y0+round(i*my*10)); //çàñå÷êè íà îñè Y
    line(x0-3,y0-round(i*my*10),x0+3,y0-round(i*my*10));
    str(i,s);
    //ïîäïèñü îñè Õ
    str(i,s);
    textout(x0+round(i*mx)-15,y0+10,s);
    textout(x0-round(i*mx),y0+10,'-'+s);
    //ïîäïèñü îñè Y
    str(i*10,s);
    textout(x0-25,y0-round(i*my*10),s);
    textout(x0-20,y0+round(i*my*10),'-'+s);
  end;
//öåíòð
textout(x0+5,y0+10,'0');
//ïîäïèñè êîíöîâ îñåé
textout(windowwidth-10,y0-15,'X');
textout(x0+5,10, 'Y');
//ãðàôèêè
setfontcolor(clGreen);
setfontsize(11);
x:=xn;
dx:=0.001;
n:=0;
while x<=xk do
 begin
  setpixel(x0+round(x*mx),y0-round(F1(x)*my),clBlue);
  setpixel(x0+round(x*mx),y0-round(F2(x)*my),clRed);
  if abs(F1(x)-F2(x))<0.0025 then //òî÷êè ïåðåñå÷åíèÿ ïîäáîðîì,
                                 //à òî èëè íå ðèñóåò èëè ðèñóåò ïî ìíîãó â îäíîì ìåñòå
   begin
    x1:=x;
    n:=n+1;
    setbrushcolor(clGreen);
    circle(x0+round(x1*mx),y0-round(F1(x1)*my),3);
    str(n,s);
    str(x1:5:2,s1);
    str(F1(x):5:2,s2);
    setbrushstyle(bsClear);
    textout(100,60+n*20,'Òî÷êà '+s+' x= '+s1+'  y='+s2)
   end;
  x:=x+dx;
 end;
if n=0 then textout(100,60,'Òî÷åê ïåðåñå÷åíèÿ íåò')
else textout(100,60,'Òî÷êè ïåðåñå÷åíèÿ');
setfontcolor(clBlue);
textout(100,20,'y=x^4');
setfontcolor(clRed);
textout(100,40,'y=2x-16');
end.