\( \dfrac{{2\sqrt 8 - \sqrt {12} }}{{\sqrt {18} - \sqrt {48} }} - \dfrac{{\sqrt 5 + \sqrt {27} }}{{\sqrt {30} - \sqrt {162} }}\\ = \dfrac{{4\sqrt 2 - 2\sqrt 3 }}{{3\sqrt 2 - 4\sqrt 3 }} - \dfrac{{\sqrt 5 + 3\sqrt 3 }}{{\sqrt {30} - 9\sqrt 2 }}\\ = \dfrac{{\left( {4\sqrt 2 - 2\sqrt 3 } \right)\left( {3\sqrt 2 + 4\sqrt 3 } \right)}}{{30}} - \dfrac{{\left( {\sqrt 5 + 3\sqrt 3 } \right)\left( {\sqrt {30} + 9\sqrt 2 } \right)}}{{ - 132}}\\ = - \dfrac{{\sqrt 6 }}{3} + \dfrac{{16\sqrt 6 + 9\sqrt {10} }}{{66}}\\ = \dfrac{{ - 22\sqrt 6 + 16\sqrt 6 + 9\sqrt {10} }}{{66}}\\ = \dfrac{{ - 6\sqrt 6 + 9\sqrt {10} }}{{66}}\\ = \dfrac{{3\left( { - 2\sqrt 6 + 3\sqrt {10} } \right)}}{{66}}\\ = \dfrac{{ - 2\sqrt 6 + 3\sqrt {10} }}{{22}} \)
mjk đang cần gấp lắm 
