## Algebra 1: Common Core (15th Edition)

In order to see if a radical is in simplified form, see if any of its factors are perfect squares (meaning that their square root will be an integer). We see that 225 has factors of 225 and 1. 225 is a perfect square, so we know that we can simplify: $\sqrt {225} = \sqrt {225} \times \sqrt {1} =15$