Kummer's Hypergeometric Theorem/Lemma 1

Lemma for Kummer's Hypergeometric Theorem

 * $\ds \lim_{y \mathop \to \infty} \dfrac {y^{\underline k} } {\paren {y + n + 1}^{\overline k} } = 1$

where $y^{\underline k}$ denotes the $k$th falling factorial of $y$.