Giải hệ phương trình (left{ {begin{array}{*{20}{c}}{3left( {x + 2} right)sqrt {x – y} = ysqrt {x – y} + 3x – y + 6,,,,,,,,,,,,,,,,,,,,,left( 1 right),,,,,,}{sqrt {3x + 1} – sqrt {5 – y} = – {x^3} + 5{x^2} + 3,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,left( 2 right),,,}end{array}} right.) – Sách Toán