The square root of 1 is 1, but the square root of 18 needs to be explored. 18 is 9*2, and 9 is a perfect square. So let's rewrite our original problem using that fact: [tex] \sqrt{ \frac{1}{18} } = \sqrt{ \frac{1}{9*2} } [/tex]. We can pull out the square root of 1 as 1 and the square root of 9 as 3, leaving the 2 behind: [tex] \sqrt{ \frac{1}{9*2} } = \frac{1}{3} \sqrt{ \frac{1}{2} } [/tex]. And there you go!