You may want to review roots and the laws of exponents first.
You can also take a root of an expression with variables. Since roots are the opposite of exponents, they follow the same rules, so √(4x6) = √4√x6. The rule for taking a root of a number raised to a power is that n√xm = xm/n, so √4√x6 = 2x3, so that's our answer. (Remember that √ means 2√.)