alternativa b
[tex] \frac{1}{ \sqrt{3} } \times \frac{ \sqrt{3} }{ \sqrt{3} } = \frac{ \sqrt{3} }{3} [/tex]
[tex] \frac{5}{2 \sqrt{5} } = \frac{5}{ \sqrt{20} } \times \frac{ \sqrt{20} }{ \sqrt{20} } = \frac{5 \sqrt{20} }{ \sqrt{400} } = \frac{5 \sqrt{20} }{20} = \frac{ \sqrt{20} }{4} = \frac{2 \sqrt{5} }{4} = \frac{ \sqrt{5} }{2} [/tex]
[tex] \frac{3}{ \sqrt{7} - 2 } \times \frac{ \sqrt{7} + 2 }{ \sqrt{7} + 2} = \frac{3 \sqrt{7} + 6}{7 + 2 \sqrt{7} - 2 \sqrt{7} - 4} = \frac{3 \sqrt{7} + 6 }{3} = \sqrt{7} + 2[/tex]
