4637. \(\frac{\sqrt{m-n}}{\sqrt{m+n}}\)

Домножим на \(\sqrt{m+n}\):

\(\frac{\sqrt{m-n}}{\sqrt{m+n}}=\frac{\sqrt{(m-n)(m+n)}}{m+n}=\frac{\sqrt{m^2-n^2}}{m+n}\).