Réponse:
[tex]1)a) \frac{1}{ \sqrt{5} - \sqrt{2} } = \frac{1( \sqrt{5} + \sqrt{2}) }{ (\sqrt{5} - \sqrt{2} )( \sqrt{5} + \sqrt{2} )} = \frac{ \sqrt{5} + \sqrt{2} }{ \sqrt{ {5}^{2} } - \sqrt{ {2}^{2} } } = \frac{ \sqrt{5} + \sqrt{2} }{5 - 2} = \frac{ \sqrt{5} + \sqrt{2} }{3} [/tex]
[tex]b) \frac{x}{ \sqrt{2x} + \sqrt{x} } = \frac{x( \sqrt{2x} - \sqrt{x}) }{( \sqrt{2x} + \sqrt{x})( \sqrt{2x} - \sqrt{x} ) } = \frac{x \sqrt{2x} - x \sqrt{x} }{2x - x} = \sqrt{2x} - x[/tex]
après simplification par x.
