Vietascher Wurzelsatz I.72

$\displaystyle \sum_{k=1}^{n}$	$\displaystyle =$	$\displaystyle -a_{n-1}$
$\displaystyle \sum_{k_{1},k_{2}=1,k_{1}\leq k_{2}}^{n}$	$\displaystyle =$	$\displaystyle a_{n-2}$
$\displaystyle \sum_{k_{1},k_{2},k_{3}=1,k_{1}\leq k_{2}\leq k_{3}}^{n}$	$\displaystyle =$	$\displaystyle -a_{n-3}$
		$\displaystyle \vdots$
$\displaystyle \prod_{k=1}^{n}z_{k}$	$\displaystyle =$	$\displaystyle \left(-1\right)^{n}a_{0}$