Question 22136
sum of GP = {{{(a(1-r^n))/(1-r)}}}. However, your series is infinite... it goes on forever. Now, if -1 < r < +1, then this formula simplifies, becoming {{{a/(1-r)}}} 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


Sum = {{{14/(1-(-1/2))}}}
Sum = {{{14/(1+1/2)}}}
Sum = {{{14/(3/2)}}}
Sum = {{{28/3}}}


which is 9 and a third.


jon.