Program Pole_pod_funkcja;
uses Graph;
var karta,tryb,n,k,iprz,j:integer;
    x,y,x1,x2,Dx,pole:real;
function f(x:real):real;
begin
  f:=(x*x*x-5*x)/5
end;
begin
  karta:=detect; initGraph(karta,tryb,'');
  j:=20;
  setColor(darkGray);
  for n:=-320 div j to 320 div j do line(320+n*j,0,320+n*j,479);
  for n:=-240 div j to 240 div j do line(0,240+n*j,639,240+n*j);
  setColor(white);
  line(0,240,639,240); line(320,0,320,479);
  setColor(lightBlue);
  x1:=-3; x2:=4;
  x:=-320/j; Dx:=0.00025;
  repeat
    x:=x+Dx;
    y:=f(x);
    if abs(y)<240/j then putPixel(round(x*j+320),round(-y*j+240),lightBlue);
    if (x>x1) and (x<x2) then line(round(x*j+320),round(-y*j+240),
                                   round(x*j+320),240);
  until x>320/j;

  setColor(lightRed);
  iprz:=20; pole:=0; Dx:=(x2-x1)/iprz;
  for n:=1 to iprz do
  begin
    x:=x1+n*Dx-Dx/2;
    pole:=pole+f(x)*Dx;
    rectangle(round(j*(x1+(n-1)*Dx)+320),round(-j*f(x)+240),
              round(j*(x1+n*Dx)+320),240);
  end;
  setColor(white); line(0,240,639,240); line(320,0,320,479);
  writeLn(' Pole = ',pole:1:4);

  readln; closeGraph;
end.