i need help with folowing

(a)$\displaystyle \frac{\sqrt{27}}{{5-{\sqrt{3}}}}$

(b)$\displaystyle \frac{{2}\sqrt{7}{-5}}{{7}\sqrt{3}{-4}}$

many thanks

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- Feb 1st 2010, 08:51 AMdecoy808Rationalise the denominators
i need help with folowing

(a)$\displaystyle \frac{\sqrt{27}}{{5-{\sqrt{3}}}}$

(b)$\displaystyle \frac{{2}\sqrt{7}{-5}}{{7}\sqrt{3}{-4}}$

many thanks - Feb 1st 2010, 09:06 AMDinkydoe
(a) $\displaystyle \frac{\sqrt{27}}{5-\sqrt{3}} = \frac{\sqrt{27}}{5-\sqrt{3}}\cdot \frac{5+\sqrt{3}}{5+\sqrt{3}}= \frac{5\sqrt{27}+\sqrt{81}}{22}$

Do the other one likewise.