Program tohop;
Uses Crt;
Var n,k:integer;
Function gt(n:integer):longint;
Var kq,i:integer;
Begin
    kq:=1;
    For i:=1 to n do
       kq:=kq*i;
    gt:=kq;
End;
Function pt(n,k:integer):real;
Begin
  pt:=gt(n)/(gt(k)*gt(n-k));
End;
Begin
   Clrscr;
   Writeln('CHUONG TRINH TINH TO HOP N CHAP K:');
   Writeln('--------------------------------');
   Write('Nhap n = '); readln(n);
   Write('Nhap k = ');readln(k);
   Writeln('C(',n,',',k,') = ',pt(n,k):6:0);
   Readln;
End.
 

chinh hop

Program chinhhop;
uses crt;
var n:integer;x:longint;
var a : longint; b:longint;
var gt:integer;
Procedure Giai_Thua(var gt:longint; n:byte);
begin
    gt:=1;
    while n>0 do
    begin
    gt:=gt*n;
    n:=n-1;
    end;
end;
Function pt(a,b:integer):real;
Begin
  pt:=gt(a)/(gt(a)*gt(a-b));
End;
begin
   repeat
   clrscr;
   if n < 0 then begin write('Nhap so n>=0');readln; end;
   until n>=0;
   Giai_Thua(x,n);
   writeln('nhap so a =') ;readln(a);
   writeln('nhap so b =');readln(b);
    Writeln('p(',a,',',b,') = ',pt(a,b):6:0);
   readln
end.