Записать уравнение параболы ( с объяснением)

Program long;
 uses Crt;
 const n=5;
 type Vec=array [1..n] of integer;
 var A, B, C: Vec;
     i,j,k, Col: integer;
     Pro: longint;
     a1, a2: integer;
begin
 ClrScr;
 Randomize;
 Col:=1;  Pro:=1;
 WriteLn ('Massiv A:');
 for i:=1 to n do
   begin
     A[i]:=500+random(2000);
     Write(A[i]:6);
     if A[i] >1000 then
        begin
          B[Col]:=A[i]; Col:=Col+1;
        end;
   end;  WriteLn;
 Col:=Col-1;  WriteLn;
 WriteLn ('Massiv B:');
 for i:=1 to Col do
   WriteLn(B[i]);
 WriteLn;
 k:=1;
 for i:=1 to n do
   begin
       a2:=B[i] mod 10;
       a1:=B[i] div 1000;
       if sqr(a1)<sqr(a2) then
           begin
              C[k]:=B[i];
              k:=k+1;
           end;
   end;
 for i:=1 to k-1 do
     Pro:=Pro*C[i];
  WriteLn ('Pro=',Pro);
ReadLn;
end.

An essay on the theme "My Motherland — Kazakhstan" I am proud of my country. This is a multi-ethnic state of Kazakhstan. It ranks ninth in world's largest site! Kazakhstan is a big state, built in a difficult environment. Are steppes, semi-deserts and deserts. Kazakhstan gained independence about twenty years ago, after the collapse of the Soviet Union. But the national culture of Kazakhstan many centuries ago began to create the Kazakhs, nomads, who spend most of life spent in the saddle. Endless steppes and semi-deserts, overgrown fescue, feather-grass, wormwood and tercica, were their only riches. Now our country is home to people of different cultures: Kazakhs, Russians, Uzbeks, Ukrainians, Uighurs, Tatars and others. Every resident of Kazakhstan knows the Kazakh language is the language of the Kazakh nation. Also recognized as the official language of Russian as language of interethnic communication. People in Kazakhstan live free, and not crowded. There are a lot of lands and people on them have a little. The majority of the people of Kazakhstan live in peace, knowing that this is our common homeland. Not in vain on may 1, the country celebrates the Day of unity of peoples of Kazakhstan, and the Christian Christmas and the Islamic Eid together are public holidays. But there are those who do not understand and creates conflicts because of religion or nationality. Although the climate in our country is considered arid and not very affectionate towards people, Kazakhstan is rich in mineral resources. In Kazakhstan there is the famous "space city" Baikonur, where the launch into space a Russian rocket. Such a unique state like Kazakhstan, is no longer anywhere in the world