Can you solve this inequality to me?

[Gilmar]

Solve in R:

x⁴- 10x² + 9 ≤ 0

[dduclam]

Solve in R:

x⁴ - 10x² + 9 ≤ 0

<=> [tex]x^4-x^2-9x^2+9\le0[/tex]

<=> [tex]x^2(x^2-1)-9(x^2-1) \le0[/tex]

<=> [tex](x^2-9)(x^2-1)\le0[/tex]

<=>[tex]1\le x^2\le9[/tex]

<=> [tex]1\le x\le3[/tex] or [tex]-3\le x\le -1[/tex]