# Linear Difference Equation with Initial Conditions

$y[n] -(1/2)y[n-1]=2(-1/2)^2 u[n]$ where $u[n]$ is the unit step function at the origin and $y[-1]=3$
$Y(z)=\frac{2}{(1-0.5z^{-1})(1+0.5z^{-1})}$. I do partial fraction expansion and then I'm stuck there. How can I introduce initial conditions?!