I can give you the easy answer of 45, but let's use prime factorization.
What number looks like it divides into 2025 easily?
Your first answer was probably 5.
2025 divided by 5 is 405.
What number looks like it divides into 405 easily?
It was probably 5 again.
405 divided by 5 is 81.
Now hopefully you know that the square root of 81 is 9.
We can bring these all out of the radical.


We know that
, so we can simplify this whole expression down to the outside terms, which multiply to 45.