#include<stdio.h>
int main(){
  int a,b,c,d,x,y;
  printf("\nEnter the first complex number:");
  scanf("%d%d",&a,&b);
  printf("\nEnter the second complex number:");
  scanf("%d%d",&c,&d);
  if(b<0)
      printf("%d-i\n",a-b);
  else
      printf("d+i\n",a+b);
  if(d<0)
      printf("d-i\n",c-d);
  else
      printf("%d+i\n",c+d);
  printf("\nADDITION ");
  x=a+c;
  y=b+d;
  if(y>0)
      printf("%d-i%d",x,-y);
  else
      printf("%d+i%d",x,+y);
  printf("\n\nSUBTRACTION ");
  x=a-c;
  y=b-d;
  if(y<0)
      printf("%d-i%d",x,-y);
  else
      printf("%d+i%d",x,+y);
  return 0;
}

#include<stdio.h>
int main(){

    int n,i;
    int sum=0;

    printf("Enter the n i.e. max values of series: ");
    scanf("%d",&n);

    sum = (n * (n + 1)) / 2;

    printf("Sum of the series: ");

    for(i =1;i <= n;i++){
         if (i!=n)
             printf("%d + ",i);
         else
             printf("%d = %d ",i,sum);
         }
   
    return 0;
}
Sample output:
Enter the n i.e. max values of series: 5
Sum of the series: 1 + 2 + 3 + 4 + 5 = 15

#include<stdio.h>

int main(){

    int n,i;
    int sum=0;

    printf("Enter the n i.e. max values of series: ");
    scanf("%d",&n);

    sum = (n * (n + 1) * (2 * n + 1 )) / 6;

    printf("Sum of the series : ");

    for(i =1;i<=n;i++){
         if (i != n)
             printf("%d^2 + ",i);
         else
             printf("%d^2 = %d ",i,sum);
    }

    return 0;
}
Sample output:
Enter the n i.e. max values of series: 5
Sum of the series: 1^2 + 2^2 + 3^2 + 4^2 + 5^2 = 55

#include<stdio.h>
#include<math.h>

int main(){

    int n,i;
    int sum=0;

    printf("Enter the n i.e. max values of series: ");
    scanf("%d",&n);

    sum = pow(((n * (n + 1) ) / 2),2);

    printf("Sum of the series : ");

    for(i =1;i<=n;i++){
         if (i != n)
             printf("%d^3 + ",i);
         else
             printf("%d^3 = %d ",i,sum);
    }

    return 0;
}
Sample output:
Enter the n i.e. max values of series: 3
Sum of the series: 1^3 + 2^3 + 3^3 = 36

#include<stdio.h>
#include<math.h>

int main(){

    int a,d,n,i,tn;
    int sum=0;

    printf("Enter the first number of the A.P. series: ");
    scanf("%d",&a);

    printf("Enter the total numbers in the A.P. series: ");
    scanf("%d",&n);

    printf("Enter the common difference of A.P. series: ");
    scanf("%d",&d);

    sum = ( n * ( 2 * a + ( n -1 ) * d ) )/ 2;
    tn = a + (n-1) * d;
    printf("Sum of the series A.P.: ");

    for(i=a;i<=tn; i= i + d ){
         if (i != tn)
             printf("%d + ",i);
         else
             printf("%d = %d ",i,sum);
    }

    return 0;
}
Sample output:
Enter the first number of the A.P. series: 1
Enter the total numbers in the A.P. series: 5
Enter the common difference of A.P. series: 3
Sum of the series: 1 + 4 + 7 + 10 + 13 = 35