Sum of series k^2-k

Given number:
$$k^{2} - k$$
It is a series of species
$$a_{k} \left(c x - x_{0}\right)^{d k}$$
- power series.
The radius of convergence of a power series can be calculated by the formula:
$$R^{d} = \frac{x_{0} + \lim_{k \to \infty} \left|{\frac{a_{k}}{a_{k + 1}}}\right|}{c}$$
In this case
$$a_{k} = k^{2} - k$$
and
$$x_{0} = 0$$
,
$$d = 0$$
,
$$c = 1$$
then
$$1 = \lim_{k \to \infty} \left|{\frac{k^{2} - k}{k - \left(k + 1\right)^{2} + 1}}\right|$$
Let's take the limit
we find

True

False