Решите систему уравнений (a)

$left { {{xy-3=-4x} atop {xy+6=y}} right.$
$left { {{y- frac{3}{x}=-4 } atop {y+4x=9}} right.$
$left { {{y=9-4x} atop {9-4x- frac{3}{x}=-4}} right.$
$left { {{y=9-4x} atop {9x-4 x^{2} -3=-4x}} right.$
$left { {{y=9-4x} atop {4 x^{2} -13x+3=0}} right.$
$4 x^{2} -13x+3=0$
$D=169-48=121$
$x= frac{13+- sqrt{121} }{8}$
$x_{1} =3, x_{2} =0,25$
$left { {{y=-3} atop {x=3}} right., left { {{y=7} atop {x=0,25}} right.$