$\displaystyle x^4 - 6x^2 + 8 = 0

$

$\displaystyle x^2=t$

$\displaystyle x^4=t^2$

a= 1, b = 6, c = 8

My answer using the quadratic formula:

$\displaystyle \Rightarrow x = \frac {6 \pm \sqrt {6^2 - 4(1)(8)}}{2(1)}$

$\displaystyle \Rightarrow x = \frac {6 \pm \sqrt {4}}{2}$

$\displaystyle \Rightarrow x = \frac {3 \pm \sqrt {2}}{}$

How do I reduce this further to get the final answer or is my answer correct? I always get confused. Thanks in advance.