(MACKENZIE) Para todo $\,n,p\;\in\;\mathbb{N}^*\,$, o valor de $\phantom{X}{\Large \sum\limits_{n\,=\,1}^{p}{\Large \binom{n}{n\,-\,1}}}\phantom{X}$ é, sempre,
b)
$\,{\large \frac{p(p\,+\,1)}{2}}\,$
c)
$\,{\large \binom{p\,+\,1}{p}}\,$
d)
$\,{\large \binom{p\,+\,2}{p\,-\,2}}\,$
e)
$\,{\large \binom{n\,+\,2}{n\,+\,1}}\,$
