I have this limit but have no idea how to show it. Obviously, we can plug in i for z but then we get an indeterminate form. Our professor has stated we can't use l'hospital so I was wondering if anyone had any insight. I gave also tried to factor the numerator but that does not work either.
$$
\lim\_{z\to i} \frac{iz^3-1}{z-i} 
$$