We have the following:
[tex]6x^2+144[/tex]solving:
[tex]\begin{gathered} 6x^2+144-144=-144 \\ \frac{6}{6}x^2=-\frac{144}{6} \\ x^2=-24 \\ x=\pm\sqrt[]{-24} \\ x_1=\sqrt[]{-24}=2\sqrt[]{-6}=2\sqrt[]{6}i \\ x_2=-\sqrt[]{-24}=-2\sqrt[]{-6}=-2\sqrt[]{6}i \end{gathered}[/tex]