<s>[INST] find the root : $x^8-24x^4+256x^2+144=0$ find the root of $\mathbb{R} $: 
$$x^8-24x^4+256x^2+144=0$$
my try: 
$$t=x^2\\t^4-24t^2+256t+144=0\\t^4-(8×3)t^2+(8×2^5)t+(8×18)=0$$
now ?!!
thank you very much!
 [/INST] The equation can be factored as 
$$(x^2-8x+36)(x^2+8x+4)=0$$
So here are the roots:
$$x_1 = -2(2+\sqrt{3})$$
$$x_2 = -2(2-\sqrt{3})$$
$$x_3 = 4-2\sqrt{5}i$$
$$x_4 = 4+2\sqrt{5}i$$
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