Answer:
[tex]x=3i*\sqrt{2} \\x=-3i*\sqrt{2}[/tex]
Step-by-step explanation:
Solve the associated quadratic equation to find its solutions:
[tex]x^2+18=0\\x^2=-18\\x=+/-\sqrt{-18} \\x=+/-\sqrt{-1} *\sqrt{2*9} \\\\x=+/-i *\sqrt{2} *\sqrt{9} \\\\x=+/-3i*\sqrt{2}[/tex]
