Question

tính tổng S=1-2+3-4+5-6+...+(-1)^n+1*n

Answer 1

var i,n,s:longint;

begin

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

s:=0;

for i:=1 to n do

if i mod 2 = 0 then s:=s-i

else s:=s+i;

write('Tong la ',s);

readln;

end.

Answer 2

#include <iostream>
using namespace std;
int n,s,i;
int main()
{
    s=0;
    cout<<"nhap n";cin>>n;
    for(i=1;i<=n;i++)s=s+2*i;
    cout<<"ket qua la : "<<s;
    return 0;
}