Đâu bạn... 

uses crt;

var i,n,t:integer;

begin

clrscr;

readln(n);

t:=0;

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

writeln(t);

readln;

end.

program TICHSO;

var

     n, i, j, maxVal, a_i, a_j: Integer;

begin

     maxVal := 0;

     Readln(n);

     for i := 1 to n do

     begin

          Read(a_i);

          if Abs(a_i) > maxVal then

               maxVal := Abs(a_i);

     end;

     for i := 1 to n-1 do

     begin

          for j := i+1 to n do

          begin

               a_i := Abs(a[i]);

               a_j := Abs(a[j]);

               if (a_i * a_j) > maxVal then

                    maxVal := a_i * a_j;

          end;

     end;

     Writeln(maxVal);

end.

uses crt;

var a:array[1..100]of integer;

i,n,t:integer;

begin

clrscr;

write('Nhap n='); readln(n);

for i:=1 to n do 

begin

write('A[',i,']='); readln(a[i]);

end;

t:=0;

for i:=1 to n do 

  t:=t+a[i];

writeln('Tong cac so la: ',t);

readln;

end.

tự lm kt

:)

Câu 1: B,C

Câu 2: B

program XuatSoChan;
uses crt;
const
  Max_N = 20;
type
  MangSoNguyen = array [1..Max_N] of integer;
var
  A: MangSoNguyen;
  i, n: integer;
begin
  clrscr;
  write('Nhap so luong phan tu cua mang: ');
  readln(n);
  writeln('Nhap cac phan tu vao mang:');
  for i := 1 to n do
  begin
    write('A[', i, ']: ');
    readln(A[i]);
  end;
  writeln('Cac so chan trong mang la:');
  for i := 1 to n do
  begin
    if A[i] mod 2 = 0 then
      writeln(A[i]);
  end;
  readln;
end.

(3+2) div 6 -4 = 5 div 6 -4 = 0-4=-4

uses crt;
var e,f,i,a,b,c,d: byte;
begin
clrscr;
write('Tu so = '); readln(e);
write('Mau so = '); readln(f);

a:=e;
b:=f;

writeln('Phan so ban dau: ',e,'/',f);

while E <> F do
if E > F then E:=E-F
else F:=F-E;

If e <> 1 then
begin
a:=a div e;
b:=b div e;
write('Phan so toi gian: ',a,'/',b);
end
else write('Phan so da toi gian, ',a,'/',b);
readln
end.

dùng for do thay while do dùm mình với