Question 289931
Solve for x: There will be four solutions.
{{{x^4-81x^2 = 0}}} Factor {{{x^2}}}
{{{x^2(x^2-81) = 0}}} Apply the zero product rule:
{{{x^2 = 0}}} or {{{x^2-81 = 0}}} so
{{{x = 0}}}
{{{x = 0}}}
{{{x = 9}}}
{{{x = -9}}}