[tex] \frac{ {a}^{2} - a }{a + \sqrt{2} } = \frac{( {a }^{2} - a)(a - \sqrt{2} )}{(a + \sqrt{2} )(a - \sqrt{2} )} = \frac{ {a {}^{3} } - \sqrt{2} {a}^{2} - {a}^{2} + \sqrt{2}a }{ {a}^{2} - 2} [/tex]