Use the negative exponent rules to simplify.

r^-2/r^-6

To simplify this expression using the negative exponent rules, we can apply the rule that states "When a negative exponent is in the numerator, move it to the denominator and change the sign from negative to positive."

Using this rule, we can rewrite the expression as:

r^-2/r^-6 = 1/ (r^2/r^6)

Next, we apply the rule that states "When dividing powers of the same base, subtract the exponents."

Applying this rule, we can simplify the expression further:

1/ (r^2/r^6) = 1/ (r^(2-6)) = 1/ r^(-4)

Finally, using the negative exponent rule again, we move the negative exponent from the denominator to the numerator and change the sign from negative to positive:

1/ r^(-4) = r^4

Therefore, the simplified expression is r^4.