since its a tangent we know that at the point of intersection that the x,y values are equal
thus
mx = 3 - 1/x^2
mx^3 - 3x^2 + 1 = 0 (A)
and the gradients are equal, thus the solution of (A) will be shared with its derivitive
hence
3mx^2 - 6x = 0
3x(mx-2) = 0
hence mx - 2 = 0 is...