Answer:
n = 6 , − 6
Step-by-step explanation:
Take the root of both sides and solve.
[tex]-\cfrac{1}{2}n^2+18=0\implies 18=\cfrac{1}{2}n^2\implies 18=\cfrac{n^2}{2}\implies 36=n^2 \\\\\\ \stackrel{\textit{taking }\sqrt{~~}\textit{ to both sides}}{\pm\sqrt{36}=\sqrt{n^2}}\implies \pm 6 = n[/tex]
