You can put this solution on YOUR website! sum of GP = . However, your series is infinite... it goes on forever. Now, if -1 < r < +1, then this formula simplifies, becoming and is the sum to infinity.
To find r:
-7/14 --> -1/2. This is the common ratio, r and it satisfies the condition mentioned above, so we have a=14 and r=-1/2
