If $x=9$ is a chord of contact of the hyperbola $x^2-y^2=9,$ then the equation of the tangent at one of the points of contact is

Question

$$(a)\;x+\sqrt 3\;y+2=0\quad (b)\;3x-2 \sqrt 2 \;y-3=0 \quad (c)\;3x-\sqrt 2 y+6=0\quad (d)\;x-\sqrt 3 y+2=0$$