Respuesta :

LammettHash

Factorize the numerator as a difference of squares:

[tex]x-s=(\sqrt x)^2-(\sqrt s)^2=(\sqrt x-\sqrt s)(\sqrt x+\sqrt s)[/tex]

Then

[tex]\displaystyle\lim_{x\to s}\frac{x-s}{\sqrt x-\sqrt s}=\lim_{x\to s}(\sqrt x+\sqrt s)=\boxed{2\sqrt s}[/tex]