complex numbers - What is the easiest way to get: $2+ sqrt{-121} = (2+ sqrt{-1})^3$

I was reading the book Seventeen equations have changed the world.
At some point, while the book was talking about complex numbers, I see this equation:

$2+ \sqrt{-121} = (2+ \sqrt{-1})^3$

Even if it's easy to proof the truth of this equivalence (it is enough to develop the two members),
I can't find an easy/good/fast way to obtain straight the identity.

Can you help me? Does there exist a mathematical property that I'm missing?