The square number is 1, 4,9,16,25,36,49. ...

For example, 80 is divisible by 4. You can use 16 directly if you are skilled.

Take the square root of the number divisible by it.

For example, the root number 80 can be considered as four times the root number 5.

Because 80 is equal to 16 times 5.

16 is the square of 4.

So pull out 4 and leave 5 in the root sign.