The sum of the 3rd term & 5th term of a GP is -60 and the sum of the 5th & 7th term is -240.find the common ratio

1 answer

ar^2 + ar^4 = -60
ar^4 + ar^6 = -240

ar^2 (1+r^2) = -60
ar^4 (1+r^2) = -240

-60/ar^2 = -240/ar^4
-60r^2 = -240
r = ±2