Find critical points by setting derivative equal to 0.
Derivative of polynomial is found by multiplying coefficient by exponent, then subtracting 1 from exponent.
f'(x) = 5x^4 - 30x^2 + 9 = 0
This is in quadratic form, use quadratic formula to find x^2
[tex]x^2 = \frac{15 \pm 6\sqrt{5}}{5} \\ \\
x = \pm\sqrt{\frac{15 \pm 6\sqrt{5}}{5}} = \pm 0.5628, \pm 2.384[/tex]
