Question 316777


{{{x^2=-81}}} Start with the given equation.



{{{x=""+-sqrt(-81)}}} Take the square root of both sides.



{{{x=sqrt(-81)}}} or {{{x-0=-sqrt(-81)}}} Break up the "plus/minus" to form two equations.



{{{x=9i}}} or {{{x-0=-9i}}}  Take the square root of {{{-81}}} to get {{{9i}}}. Note: {{{i=sqrt(-1)}}}



So the solutions are {{{x=9i}}} or {{{x-0=-9i}}}