[tex]\begin{gathered} \sqrt[]{9x^2} \\ \text{rewrite the expression as factors} \\ \sqrt[]{3\cdot3\cdot x\cdot x} \\ \text{pair them and get them out of the root} \\ \sqrt[]{(3^2)\cdot(x^2)}=3x \\ \text{cancel the squares} \\ \sqrt[]{9x^2}=3x \end{gathered}[/tex]
