Simplifying Square Roots That Contain Whole Numbers
In general, 4 is a factor of a number if the last two digits of the number are divisible by 4.
For example: 4 is a factor of 236 since 36 is divisible by 4.
1) In general, 9 is a factor of a number if the sum of the digits of the number is divisible by 9.
For example: 9 is a factor of 198 since 1 + 9 + 8 = 18 and 18 is divisible by 9.
2) If you realize that 36 is the largest perfect square factor of 108, the you can write: