In order to solve this exercise, you need to remember the following property for Radicals:
[tex]\sqrt[n]{a}^n=a[/tex]Notice that the Index "n" of the root and the exponent "n" inside the root are equal.
In this case you need to descompose the Radicand 9 into its Prime factors:
[tex]9=3\cdot3[/tex]According to the Product of powers property, when you multiply powers with the same base, you must copy the base and add the exponents. Then:
[tex]9=3^2[/tex]Rewrite the Radical and simplify:
[tex]\sqrt[]{9}=\sqrt[]{3^2}=3[/tex]The answer is:
[tex]=3[/tex]