If a b and c are in GP and a1/x=b1/y=c1/z, prove that x, y and z are in AP.
We have, a1/x=b1/y=c1/z=k [say]
⇒ a1/x=k, b1/y=k and c1/z=k
⇒ a=kx, b=ky and c=kz
Now, a, b and c are in GP
⇒ b2=ac
∴ (ky)2=kx.kz
⇒ k2y=kx+z
⇒ 2y=x+z
Hence, x, y and z are in AP.