# Math Help - polynomial factor

1. ## polynomial factor

Please can someone describe for me how I solve the following problem
:

Thank you!

2. $x^4+6x^2-40=0$

Let $x^2=t$

$\implies t^2+6t-40=0$

$\implies (t+10)(t-4)=0$

$\implies t=-10;~t=4$

Recall that $x^2=t$

Hence $t=\pm \sqrt{4} \implies t=\pm 2$

The other is done in the same way, so I'll let you try.