In order to solve $ \color{blue}{ 28x^{4}+22x^{2} = 0 } $, first we need to factor our $ x^2 $.
$$ 28x^{4}+22x^{2} = x^2 \left( 28x^{2}+22 \right) $$$ x = 0 $ is a root of multiplicity $ 2 $.
The remaining roots can be found by solving equation $ 28x^{2}+22 = 0$.
$ 28x^{2}+22 = 0 $ is a quadratic equation.
You can use step-by-step quadratic equation solver to see a detailed explanation on how to solve this equation.