#include "stdio.h"
#include "conio.h"
float gt(int *n)
{
     int i;
     long int gt=1;
     if ( n==0) return(1);
      else
    for (i=2;i<=*n;i++)
        gt=gt*i;
    return(gt);
}
/*
float xuli(int *n)
{
      float temp;
      int i;
      if (*n%2==1)
      i=1;
       else i=-1;
      temp=i/giaithua(n);
      return(temp);
}
*/
main()
{
      int i,n;
      float temp,sum=0;
      printf("nhap n\t");
      scanf("%d",&n);
     //
      // de: 1-1/2!+1/3!+....- (-1)^(2n+1)/n!
      for (i=1;i<=n;++i)
     
        {
                       temp=(1/gt(&i));
                              
                          if (i%2 == 1)
                             { printf("\n\ti=%d\tsum =%f\ttemp=%f",i,sum,temp);
                                  sum=sum+temp;
                             }
                      else
                             { printf("\n\ti=%d\tsum =%f\ttemp=%f",i,sum,temp);
                                sum=sum-temp;
                           }
         }            
      printf("\ntong la %f",sum);
      getch();
     
}

          

 

write by language c++
#include "stdio.h"
#include "conio.h"
#include <iostream.h>
#include <stdlib.h>
float gt(int *n)
{
     int i;
     long int gt=1;
     if ( n==0) return(1);
      else
    for (i=2;i<=*n;i++)
        gt=gt*i;
    return(gt);
}

int main()
{
      int i,n;
      float temp,sum=0;
      cout<<"\nnhap n";
      cin >>n;
     //
      // de: 1-1/2!+1/3!+....- (-1)^(2n+1)/n!
      for (i=1;i<=n;++i)
     
        {
                       temp=(1/gt(&i));
                              
                          if (i%2 == 1)
                             {
                                  cout<<"\ni =  "<<i<<"sum = "<<sum<<"temp= "<<temp;// có the bo qua
                                  sum=sum+temp;
                             }
                      else
                           {
                                  cout<<"\ni =  "<<i<<"sum = "<<sum<<"temp= "<<temp;//co the bo
                                sum=sum-temp;
                           }
         }            
      cout<<"\ntong la "<<sum;
      getch();
    return(0); 
}