How would you explain to a seventh grader the difference between the domains of an odd root radical function and an even root radical function?

To start with, when you multiply an even number of negative numbers, the answer is positive. When you multiply an odd number of negative numbers, the answer is negative. When you multiply any number of positive numbers, the answer is always positive. For positive numbers, the value of a power is always positive. For negative numbers, the value of an odd power is negative, and the value of an even power is positive. Finding roots is the inverse of taking powers, so that an odd-root function can be evaluated for any value of x. An even-root function, however, cannot be evaluated when the value of x is negative, since an even power can never result in a negative answer. The domain of an odd root function is all real numbers; the domain of an even root function is the non-negative real numbers.