Câu 2:

for .... do

Phần khai báo bạn tự làm :)

begin

clrscr;

writeln('Nhap N: ');readln(N);

tong:=0;

for i: = 1 to N do Tong:=Tong+i;

writeln('Tong cua ',N,' so tu nhien dau tien la: ',Tong);

readln;

end.

while ... do

begin

clrscr;

write('Nhap N: ');readln(N);

Tong:=0;i:=1;

while i<=N do

begin

   Tong:=Tong+i;

   i:=i+1

end;

writeln('Tong cua ',N,' so tu nhien dau tien la: ',Tong);

readln;

end.

Nhớ vote mik 5 sao :)

Bài 2a:

Program FNG;
Uses crt;
Var n,i,s: longint;
Begin
        Clrscr;
        Write('Nhap n: '); Readln(n);
        s:=0;
        For i:=1 to n do
                s:=s+i;
        Write('S = ',s);
        Readln
End.

b)

Program FNG;
Uses crt;
Var n,i,s: longint;
Begin
        Clrscr;
        Write('Nhap n: '); Readln(n);
        s:=0; i:=1;
        While i<=n do
        Begin
                s:=s+i;
                inc(i);
        End;
        Write('S = ',s);
        Readln
End.