dkxd: a, b ≥ 0; a≠9;b≠25
\(\left(2-\dfrac{a-3\sqrt{a}}{\sqrt{a}-3}\right)\left(2-\dfrac{5\sqrt{a}-\sqrt{ab}}{\sqrt{b}-5}\right)=\left(2-\dfrac{\sqrt{a}\left(\sqrt{a}-3\right)}{\sqrt{a}-3}\right)\left(2+\dfrac{\sqrt{a}\left(5-\sqrt{b}\right)}{5-\sqrt{b}}\right)=\left(2-\sqrt{a}\right)\left(2+\sqrt{a}\right)=4-a\)
\(\left(2-\dfrac{a-3\sqrt{a}}{\sqrt{a}-3}\right)\left(2-\dfrac{5\sqrt{a}-\sqrt{ab}}{\sqrt{b}-5}\right)=\left[2-\dfrac{\sqrt{a}\left(\sqrt{a}-3\right)}{\sqrt{a}-3}\right]\left[2+\dfrac{\sqrt{a}\left(5-\sqrt{b}\right)}{5-\sqrt{b}}\right]=\left(2-\sqrt{a}\right)\left(2+\sqrt{a}\right)=4-a\)