When \(a \ne 0\), there are two solutions to \(ax^2 + bx + c = 0\) and they are \[x = {-b \pm \sqrt{b^2-4ac} \over 2a}.\]

$$ \boxed{\vec{P}= m \vec{g}}$$ \\ Valori del modulo di $\vec{g}$, a tre cifre significative:\\ $g = 9,81 \UMbox{N/kg}$\\