To prove:

Given: a, b, c are in GP

Formula used: When a,b,c are in GP, b² = ac

a, b, c are in GP,

⇒ b² = ac … (i)

… (ii)

Taking LHS =

Substituting the value b² = ac from eqn. (i)

LHS =

Substituting the value b = from eqn. (ii)

Multiplying and dividing with

⇒

⇒ = RHS

Hence Proved