Question

S=2+4+6+8+.....+2n(n số tự nhiên nhập từ bàn phím)

Answer 1

program tinh_tong ;

var i, n: integer; S: longint;

begin

clrscr;

writeln('Moi ban nhap n'); readln(n);

S:=0;

for i:= 1 to n do S:= S + 2*i;

writeln (' tong S la: ', S);

readln;

end.

Answer 2

program tinh_tong;

uses crt;

var j,k,i,n:integer;

s:real;

begin

clrscr;

repeat

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

if n>=1 then break;

writeln('Hay nhap n>=1');

until false;

s:=0;

for i:=1 to n do

s:=s+2*i;

writeln('Tong: ',s:4:2);

readln

end.