Since the constant term does not matter in terms of whether the series converges or diverges, we can ignore it and hence the equation can be written as:
Here z(t) = y(t)-1
Now, the relevant polynomial becomes p(x) = 1-0.5x+0.3x^2;
To check whether the model is invertible or not, we compute the roots of p(x) = 0 using the roots method.
Hope this helps!