I want to solve this difference equation, using the z-transforms.
Using a table I get that:
$x_{n+1}\rightarrow zX(z)$
$2x_n\rightarrow 2X(z)$
but then I cannot find any entry for $-n^3$. Using WA this transform is meant to be
$-\frac{(z (1 + 4 z + z^2))}{(-1 + z)^4}$
But how is this found using a table? I thought of using the definition
$\sum_0^\infty -\frac{n^3}{z^k}$, but I am not sure how this turns into the WA result.
Any ideas?
Thanks