1/

Program BTH;
uses crt;
var s,n,i:longint;
Begin
        clrscr;
        write('Nhap n: ');readln(n);
        For i:=1 to n do
        Begin
                s:=s+i;
        end;
        Writeln('Tong day so tren la: ',s);
        readln;
end.

2/

Program BTH;
uses crt;
var s,n,i:longint;
Begin
        clrscr;
        write('Nhap n: ');readln(n);
        For i:=1 to n do
        Begin
                s:=s+i*i;
        end;
        Writeln('Tong day so tren la: ',s);
        readln;
end.

3/

Program BTH;
uses crt;
var s,n,i:longint;
Begin
        clrscr;
        write('Nhap n: ');readln(n);
        For i:=1 to n-1 do
        Begin
                if i mod 2=0 then
                s:=s+i;
        end;
        Writeln('Tong day so tren la: ',s);
        readln;
end.

Bài 1:

Program bai1;

Uses crt;

Var i,n: integer;

    Tich: real;

Begin

clrscr;

Write(' Nhap gia trị n: '); readln(n);

Tich:=Tich+1;

For i:=1 to n do Tich:=Tich*i;

Writeln(' Tich cac so nguyen la: ',Tich:6:2);

Readln

End.

Bài 2:

Program bai2;

Uses crt;

Var i,n,S: integer;

Begin

clrscr;

Write('Nhap gia tri n: '); readln(n);

S:=0;

For i:=1 to n do S:=S+i*i;

Writeln(' Tong binh phuong cua day la: ',S);
Readln
End.

Bài 3:

Program bai3;

Uses crt;

Var S,i,n : integer;

Begin

clrscr;

Write(' Nhap gia trị n: '); readln(n);

S:=0;

For i:=1 to n-1 do 

     If i mod 2 = 0 then S:=S+i;

Writeln(' Tong cac so chan la ',S);

Readln

End.