No, that's not quite right. The rule for multiplying radicals with different signs in the denominator is: If the denominators are the same sign (either both positive or both negative), then the result is positive. If the denominators have different signs (one positive and one negative), then the result is negative. So, the rule doesn't depend on whether the denominator is already positive or negative - it depends on the relationship between the signs of the two denominators.
