uses graph crt var driver mode xp integer x_t real tic string sqr sqr

uses graph,crt;

var driver, mode,xp,x,y :integer;
    x_t                 :real;
    tic                 :string;

// (sqr(x)+x+1)/(sqr(x)-x+1);

function y_global(y:real):integer;
begin
        if y<0 then
                y_global:=240+trunc(abs(y*50))
        else
                y_global:=240-trunc(abs(y*50));
end;

function x_global(x:real):integer;
begin
        if x<0 then
                x_global:=240-trunc(abs(x*(630/8)))
        else
                x_global:=240+trunc(abs(x*(630/8)));
end;

begin
        Driver:=VGA;
        Mode:=VGAHi;// 640x480
        InitGraph(Driver, Mode, 'C:\program files\FPC');

        //axis
        Line(240,0,240,480);
        Line(00,240,640,240);

        for y:=-4 to 4 do begin
                str(y,tic);
                if y<>0 then begin
                MoveTo(x_global(0),  y_global(y));
                LineTo(x_global(0)+5,y_global(y));
                outtextxy(x_global(0)+8, y_global(y), tic);
                end;
        end;

        for x:=-3 to 5 do begin
            x_t:=x;
            while x_t<=x+1 do begin
                xp:=x_global(x_t);
                PutPixel( xp, y_global((sqr(x_t)+x_t+1)/(sqr(x_t)-x_t+1)), red );
                x_t:=x_t+0.001;
            end;
            MoveTo(x_global(x),240);
            LineTo(x_global(x),245);
            str(x,tic);
            outtextxy(x_global(x)+3, 250, tic);
        end;

        readln;
        CloseGraph;
end.