Question 168496
{{{f(x) = x^4-18x^2+32}}} Factor the trinomial and set the function equal to zero.
{{{(x^2-16)(x^2-2) = 0}}} Apply the zero product rule.
{{{x^2-16 = 0}}} or {{{x^2-2 = 0}}}
If {{{x^2-16 = 0}}} then {{{x^2 = 16}}} so {{{x = 4}}} or {{{x = -4}}}
If {{{x^2-2 = 0}}} then {{{x^2 = 2}}} so {{{x = sqrt(2)}}} or {{{x = -sqrt(2)}}}
The zeros are:
{{{x = 4}}}
{{{x = -4}}}
{{{x = sqrt(2)}}} 
{{{x = -sqrt(2)}}}
See the graph below as a confirmation.
{{{graph(400,400,-5,5,-50,35,x^4-18x^2+32)}}}