\[\begin{array}{l} A\left( { - \frac{{\sqrt {378 + 84\sqrt {21} } }}{{28}}, - \frac{{\sqrt { - 378 + 84\sqrt {21} } }}{{28}}} \right) \hfill \\ B\left( {\frac{{\sqrt {42 + 28\sqrt {21} } }}{{28}},\frac{{\sqrt { - 42 + 28\sqrt {21} } }}{{28}}} \right) \hfill \\ \left| {AB} \right| = \sqrt[4]{{\frac{{21}}{4}}} \hfill \\ AB:y = \frac{{\sqrt 7 - 2\sqrt 3 }}{5} \cdot x + \frac{3}{{2\sqrt {27 + 7\sqrt {21} } }} \hfill \\ \end{array} \]