If a, b, c are the pth, qth and rth terms of a GP, show that (q – r) log a + (r – p) log b + (p – q) log c = 0.
If a, b, c are the pth, qth and rth terms of a GP, show that (q – r) log a + (r – p) log b + (p – q) log c = 0.

Answer : As per the question, a, b and c are the pth, qth and rth term of GP. Let us assume the required GP as A, AR, AR2, AR3…

Now, the nth term in the GP, an = ARn-1 pth term, ap = ARp-1 = a → (1)

qth term, aq = ARq-1 = b → (2) rth term, ar = ARr-1 = c → (3)