Write a C program to read in two numbers, x and n, and then compute the sum of this geometric progression:
For example: if n is 3 and x is 5, then the program computes 1+5+25+125.
Print x, n, the sum
Perform error checking. For example, the formula does not make sense for negative exponents – if n is less than 0.
Have your program print an error message if n<0, then go back and read in the next pair of numbers of without computing the sum. Are any values of x also illegal? If so, test for them too.


Step 1: Start
Step 2: read values of x and n, sum - 1, i = 1
Step 3: check for n & X
           i) if n <= 0 || x <= 0
           ii) print values are not valid
           iii) read values of x and n
Step 4: perform the loop operation
            i) for(i = 1; i <= n; i++) then follows
            ii) sum=sum+pow(x, i)
Step 5: print sum
Step 6: Stop


#include <stdio.h>
#include <conio.h>
#include <math.h>
void main()
   int n, x, i, sum = 0;
   printf("Enter the limit\n");
   scanf("%d", &n);
   printf("Enter the value of x\n");
   scanf("%d", &x);
   if(x < 0 || n < 0)
      printf("illegal  value");
      for(i = 0; i <= n; i++)
      sum=sum + pow(x, i);
   printf("sum=%d", sum);

Input & Output:

Enter the limit  
Enter the value of x