a/ \(\sqrt 3x-\sqrt 2x=\sqrt 2+\sqrt 3\\↔x(\sqrt 3-\sqrt 2)=\sqrt 2+\sqrt 3\\↔x=\dfrac{\sqrt 2+\sqrt 3}{\sqrt 3-\sqrt 2}\)\\↔x=5+2\sqrt 6\)
Vậy \(S=\{5+2\sqrt 6\}\)
b/ \(3\sqrt 5 x+\sqrt {20} x-\sqrt 5=0\\↔x(3\sqrt 5+\sqrt{20})=\sqrt 5\\↔x=\dfrac{\sqrt 5}{3\sqrt 5+\sqrt{20}}\\↔x=0,2\)
Vậy \(S=\{0,2\}\)
c/ \(\sqrt{\dfrac{2}{3}}x-\sqrt 6=0\\↔\sqrt{\dfrac{2}{3}}x=\sqrt 6\\↔x=3\)
Vậy \(S=\{3\}\)