So to find the root, we have to remember the Laws of Exponents for this problem.
1st, we can separate the radicand (everything under the root sign) as two different bases: 625*x20. So the problem now looks like 4√625 * 4√x20
2nd, because of the Laws of Exponents, we know that the 4√ of x is just x1/4. So we can change 4√625 *
4√x20 to (625)1/4 * (x20)1/4.
3rd, now we can simplify the problem, again using the Law of Exponents. (625)1/4=5 and (x20)1/4=x20/4. So the entire problem looks like 5*x20/4, which equals 5x5.
So your answer is 5x5
Hope this helps and makes sense too.