CÂU 1:

program ct;

uses crt;

var i,n:integer;

begin

clrscr;

write('nhap n:=');readln(n);

if n<=1 then writeln('N khong la so nguyen to') else

begin

i:=2;

while (n mod i<>0) do i:=i+1;

if i=n then writeln(n,' la so nguyen to'); else

writeln(n,'khong la so nguyen to');

end;

readln

end.

CÂU 2:

program ct;

uses crt;

var i,n:integer;

begin

clrscr;

write('nhap n:=');readln(n);

for i:=1 to n do

if i mod 2=0 then write(i);

readln

end.

CÂU 3:

program ct;

uses crt;

var n,i,s:integer;

begin

clrscr;

write('nhap n:=');readln(n);

s:=0;

for i:=1 to n do s:=s+i;

writeln('tong cua n so tu nhien la:',s);

readln

end.

Bài 1:

program bai_giai;
uses crt;
var n,i,d:integer;
begin
    clrscr;
    write('Nhap n: ');  readln(n);
    d:=0;
    for i:=2 to n div 2 do
        if n mod i=0 then d:=d+1;
    if d=0 then write('La so nguyen to') else write('Khong phai');
    readln;
end.

Bài 2:

program bai_giai;
uses crt;
var n,i:integer;
begin
    clrscr;
    write('Nhap n: ');  readln(n);
    for i:=2 to n do
        if i mod 2=0 then write(i,' ');
    readln;
end.

Bài 3:

program bai_giai;
uses crt;
var n,i,t:integer;
begin
    clrscr;
    write('Nhap n: ');  readln(n);
    for i:=2 to n do t:=t+i;
    write(t);
    readln;
end.