2y[n-2]-2y[n-3]-4y[n-4]=x[n]-10x[n-1]-4x[n-2] + 4x[n-3]  is the system that I'm looking for the response.

I transformed this system via using Z transform:

    Y(Z)    z^4 - 10z^3 - 4z^2 + 4z
    ---- = --------------------------
    X(Z)         2( z^2 -z -2 )


H(Z) = 0.5z^2 -4z -5(1/(z-2)) -1/3(1/(z-2)) +1/3(1/(z+1))

How to find ROC to inverse the Z transfom to h[n]?