The roots of polynomial $ p(x) $ are:
$$ \begin{aligned}x_1 &= 0\\[1 em]x_2 &= \frac{\sqrt{ 3 }}{ 3 }i\\[1 em]x_3 &= - \frac{\sqrt{ 3 }}{ 3 }i \end{aligned} $$Step 1:
Write polynomial in descending order
$$ \begin{aligned} x^2+3x^4 & = 0\\[1 em] 3x^4+x^2 & = 0 \end{aligned} $$Step 2:
Factor out $ \color{blue}{ x^2 }$ from $ 3x^4+x^2 $ and solve two separate equations:
$$ \begin{aligned} 3x^4+x^2 & = 0\\[1 em] \color{blue}{ x^2 }\cdot ( 3x^2+1 ) & = 0 \\[1 em] \color{blue}{ x^2 = 0} ~~ \text{or} ~~ 3x^2+1 & = 0 \end{aligned} $$One solution is $ \color{blue}{ x = 0 } $. Use second equation to find the remaining roots.
Step 3:
The solutions of $ 3x^2+1 = 0 $ are: $ x = \dfrac{\sqrt{ 3 }}{ 3 } i ~ \text{and} ~ x = - \dfrac{\sqrt{ 3 }}{ 3 } i $.
You can use step-by-step quadratic equation solver to see a detailed explanation on how to solve this quadratic equation.