[tex]\displaystyle \frac{7}{ \sqrt{3} }= \frac{7 \sqrt{3} }{3} \\ \\ \frac{2}{5 \sqrt{2} } = \frac{2 \sqrt{2} }{5 \cdot 2} = \frac{2 \sqrt{2} }{10} = \frac{ \sqrt{2} }{5} \\ \\ \frac{1}{2- \sqrt{3} } = \frac{2+ \sqrt{3} }{4-3} =2+ \sqrt{3} \\ \\ \frac{5}{1+ \sqrt{3} }= \frac{5(1- \sqrt{3} )}{1-3} = \frac{5-5 \sqrt{3} }{-2} =- \frac{5-5 \sqrt{3} }{2} [/tex]
