check the links in the comments above, notice on all those links, we multiply top and bottom always by the same value, it being the conjugate pair or just a rational or something else, is the same value atop and below.
now, what is same over same?
![\bf \cfrac{same}{same}\implies \cfrac{spaghetti}{spaghetti}\implies \cfrac{\textit{frying pan}}{\textit{frying pan}} \\\\\\ \cfrac{√(3x^3-y^4)}{√(3x^3-y^4)}\implies \cfrac{\log_5(z^e)}{\log_5(z^e)}\implies \boxed{1}](https://img.qammunity.org/2020/formulas/mathematics/college/szdn3wf9nppxcveflgozrvucxnsqyl9vpz.png)
so you see, we're really always multiplying the fraction by 1, so its top and bottom are just 1 in disguise.