Concept:
- If a, b and c are three terms in GP then b2 = ab and vice-versa
- If three terms a, b, c are in HP, then
and vice-versa - When three quantities are in AP, the middle one is called as the arithmetic mean of the other two.
- If a, b and c are three terms in AP then

- and vice-versa
- If a, b and c are in A.P then 1/a, 1/b, 1/c are in H.P and vice-versa
Calculation:
(b + c), (c + a) and (a + b) are in A.P
⇒ 2(c + a) = b + c + a + b
⇒ 2c + 2a = 2b + a + c -----(i)
⇒ 2c + 2a - 2b - a - c = 0
⇒ 2b = c + a
So, a, b, c are in AP
Now, Let (b + c)2, (c + a)2, (a + b)2 are in GP
(c + a)2 = √[(b + c).(a + b)]2
⇒ c2 + a2 + 2ac = (b + c).(a + b)
⇒ c2 + a2 + 2ac = ab + b2 + ac + bc
⇒ c2 + a2 - b2 + ac - ab - bc = 0
From here we are unable to check the relation between a, b and c
So, Our assumption was wrong
So, (b + c)2, (c + a)2, (a + b)2 are not in GP.