# Find the sum of series 3, -6, 12, -24 . . . upto N terms

Given an integer N. The task is to find the sum upto N terms of the given series:

3, -6, 12, -24, … upto N terms

Examples:

Input : N = 5
Output : Sum = 33

Input : N = 20
Output : Sum = -1048575


## Recommended: Please try your approach on {IDE} first, before moving on to the solution.

On observing the given series, it can be seen that the ratio of every term with their previous term is same which is -2. Hence the given series is a GP(Geometric Progression) series.

So, when r < 0.

In above GP series the first term i:e a = 3 and common ratio i:e r = (-2).

Therefore, .
Thus, .

Below is the implementation of above approach:

## C++

 //C++ program to find sum upto N term of the series:  // 3, -6, 12, -24, .....     #include  #include  using namespace std;  //calculate sum upto N term of series     class gfg  {      public:      int Sum_upto_nth_Term(int n)      {          return (1 - pow(-2, n));      }  };  // Driver code  int main()  {      gfg g;      int N = 5;      cout<

## Java

 //Java program to find sum upto N term of the series:  // 3, -6, 12, -24, .....     import java.util.*;  //calculate sum upto N term of series     class solution  {     static int Sum_upto_nth_Term(int n)  {      return (1 -(int)Math.pow(-2, n));  }     // Driver code  public static void main (String arr[])  {      int N = 5;      System.out.println(Sum_upto_nth_Term(N));  }     } 

## Python

 # Python program to find sum upto N term of the series:  # 3, -6, 12, -24, .....     # calculate sum upto N term of series  def Sum_upto_nth_Term(n):      return (1 - pow(-2, n))     # Driver code  N = 5 print(Sum_upto_nth_Term(N)) 

## C#

 // C# program to find sum upto   // N term of the series:  // 3, -6, 12, -24, .....     // calculate sum upto N term of series  class GFG  {     static int Sum_upto_nth_Term(int n)  {      return (1 -(int)System.Math.Pow(-2, n));  }     // Driver code  public static void Main()  {      int N = 5;      System.Console.WriteLine(Sum_upto_nth_Term(N));  }  }     // This Code is contributed by mits 

## PHP

  

Output:

33
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