Can the numerator and denominator in the result of fractional operation be in the form of product or polynomial? Is there any unified regulation?

Can the numerator and denominator in the result of fractional operation be in the form of product or polynomial? Is there any unified regulation?

In the result of fractional operation, the numerator and denominator can be in the form of product or polynomial. There is no uniform regulation. As long as the result is the simplest and meaningful (denominator is not zero), it is OK