From given A.P i.e., a b2 c3, a2 b3 c4, a3 b4 c5, get the value of abc
Observe that a + b + c is a part of AM of a, b, c i.e., (a+b+c)3 as AM ≥ GM & HM,
We can get minimum value of AM from this relation : AM ≥ GM
Using AM ≥ GM ⇒ a + b + c ≥ 3 (abc)13 ------------(1)
We need value of abc
Given a b2 c3, a2 b3 c4, a3 b4 c5 are in A.P.
2a2b3c4ab2c3 = ab2c3ab2c3 + a3b4c5ab2c3
⇒ 2abc = 1 + a2 b2 c2
⇒ (abc)2 - 2abc + 1 = 0
⇒ (abc−1)2 = 0
So, abc = 1