The amplitude of wave disturbance propagating in the positive x-direction is given by $y = {1 \over {{{(1 + x)}^2}}}$ at time t = 0 and $y = {1 \over {1 + {{(x - 2)}^2}}}$ at t = 1 s, where x and y are in metres. The shape of wave does not change during the propagation. The velocity of the wave will be ___________ m/s.