If a, b, and c be three distinct real numbers in G.P. and a + b + c = xb, then x cannot be 4

Let a, b, br be in G.P. (|r| ≠ 1)
given a + b + c = xb
⇒ br + b + br = xb
⇒ b(r + 1 + 1/r) = xb
⇒ b = 0 (not possible) or 1 + r + 1/r = x
⇒ x = r + 1/r
⇒ x ≥ 2 or x ≤ -2
⇒ x > 2 or x < -2
So x can't be 2.