Bài 2

Tính S(n) = 1^2 + 2^2 + 3^3 + ... + n^2

//========================================
//Cách 1

#include <stdio.h>
#include <conio.h>

void main()
{
 int n;
 printf("n = ");
 scanf("%d", &n);
 long S = 0;
 int i = 1;
 while (i <= n)
 {
  S = S + i*i;
  i = i + 1;
 }
 printf("S = %ld", S);
}

//========================================
//Cách 2

#include <stdio.h>
#include <conio.h>

long Tong(int);
void main()
{
 int n;
 printf("n = ");
 scanf("%d", &n);
 long kq = Tong(n);
 printf("S = %ld", kq);
}

long Tong(int k)
{
 int S = 0;
 for (int i=1; i<=k; i++)
 {
  S = S + i*i;
 }
 return S;
}