To simplify the radical, factorize the number under it using the prime number
Since 252 is an even number, then let us divide it by the 1st prime number 2

since 126 is an even number, then divide it by 2 again

Now 63 is an odd number and sum of its digit = 6 + 3 = 9, then
Divide it by the 2nd prime number 3

Since 21 is divisible by 3, divide it by 3 again

Then 252 = 2 x 2 x 3 x 3 x 7, put them under the radical
![\sqrt[]{252}=\sqrt[]{2*2*3*3*7}](https://img.qammunity.org/2023/formulas/mathematics/college/63d5trgie7u0kfvv7f57ll8t7xknf3bv26.png)
Each number repeated twice can go out the radical, then
2 and 3 will go out the radical
![\begin{gathered} \sqrt[]{252}=2*3*\sqrt[]{7} \\ \sqrt[]{252}=6\sqrt[]{7} \end{gathered}](https://img.qammunity.org/2023/formulas/mathematics/college/e3vqr7e667j6cfgbx113yf2239fw7vidfu.png)
The simplest form of the radical is 6 square root 7
![\begin{gathered} \sqrt[]{252}=\sqrt[]{4}*\sqrt[]{63} \\ =2*\sqrt[]{63} \\ =2*\sqrt[]{9}*\sqrt[]{7} \\ =2*3*\sqrt[]{7} \\ =6*\sqrt[]{7} \\ =6\sqrt[]{7} \end{gathered}](https://img.qammunity.org/2023/formulas/mathematics/college/sr68r775shi80eeuzg9ibvqxy6mo489blj.png)