Ответ:
\[- \frac{1}{2}xy;\ \ x = \sqrt{6};\ \ y = \sqrt{24}:\]
\[- \frac{1}{2}\sqrt{6 \cdot 24} = - \frac{1}{2}\sqrt{144} =\]
\[= - \frac{1}{2} \cdot 12 = - 6.\]
\[- \frac{1}{2}xy;\ \ x = \sqrt{6};\ \ y = \sqrt{24}:\]
\[- \frac{1}{2}\sqrt{6 \cdot 24} = - \frac{1}{2}\sqrt{144} =\]
\[= - \frac{1}{2} \cdot 12 = - 6.\]