Question 21699
Solve by factoring:
{{{3x^4 - 75x^2 = 0}}} Factor out 3x^2
{{{3x^2(x^2 - 25) = 0}}} Apply the zero product principle.
{{{3x^2 = 0}}} and/or {{{x^2 - 25 = 0}}}
If {{{3x^2 = 0}}} then, x = 0
If {{{x^2 - 25 = 0}}} then, {{{x^2 = 25}}} and x = +5 or x = -5

The roots are:
x = 0 A double root.
x = 5
x = -5 

Here's what the graph looks like.

{{{graph(300,200,-7,7,-500,10,3x^4-75x^2)}}}