Out of four number in a sequence,first three are in GP with first term 2 and last three are in AP with common difference 12. Find the common ratio, if the number are positive.
3
t1 = 2r
t2 = 2r
t3 = 2r2
There are the first three terms which are in GP last three terms in AP are
T2 = 2
T3 = 2r + 12
T4 = 2r + 24
Equating t3 in AP and GP
2r + 12 = 2r2
r2 - r - 6 = 0
(r - 3) (r + 2) = 0 ⇒ r = 3 [r is +ive]