The roots of polynomial $ p(s) $ are:
$$ \begin{aligned}s_1 &= \sqrt{ 6 }i\\[1 em]s_2 &= -\sqrt{ 6 }i \end{aligned} $$The solutions of $ s^2+6 = 0 $ are: $ s = \sqrt{ 6 } i ~ \text{and} ~ s = -\sqrt{ 6 } i $.
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