[tex]\sqrt{\dfrac{18y}{36y^3}}=\sqrt{\dfrac{18y}{18y\cdot2y^2}}=\sqrt{\dfrac{1}{2y^2}}=\dfrac{\sqrt1}{\sqrt{2y^2}}=\dfrac{1}{\sqrt2\cdot\sqrt{y^2}}=\dfrac{1}{y\sqrt2}[/tex]
[tex]\dfrac{1}{y\sqrt2}=\dfrac{1}{y\sqrt2}\cdot\dfrac{\sqrt2}{\sqrt2}=\dfrac{\sqrt2}{2y}[/tex]
