Given ω=z−31iz and ∣ω∣=1∴z−31i∣z∣=∣ω∣⇒z−31i∣z∣=1⇒∣z∣=z−31i........... equation (1) ∣z∣ represent distance of z from point (0,0) and z−31i represent distance of z from point (0,31). According to the equation (1) the distance of z from point (0,0) and (0,31) is equal. Only if z is on a straight line then it will be equal distance from the both the points.