Answer: [tex]\large \boldsymbol{} \pmb{6\sqrt{2} i}[/tex]
Step-by-step explanation:
[tex]\large \boldsymbol{} \bf i=\sqrt{-1} \\\\ 2n^2=-144 \\\\n^2=-72 \\\\n=6\sqrt{2} i[/tex]
[tex]\\ \sf\longmapsto 2n^2=-144[/tex]
[tex]\\ \sf\longmapsto n^2=\dfrac{-144}{2}[/tex]
[tex]\\ \sf\longmapsto n^2=-72[/tex]
[tex]\\ \sf\longmapsto n=\sqrt{-72}[/tex]
[tex]\\ \sf\longmapsto n=8.4i[/tex]