σw-W=z⁢(z-1)⁢W′W⁡(W-1)⁢(W-z)+Θ0W+Θ1W-1+Θ2-1W-z=z⁢(z-1)⁢w′w⁡(w-1)⁢(w-z)+θ0w+θ1w-1+θ2-1w-z.