3. The curve \(C\) has equation
$$3 y ^ { 2 } - 11 x ^ { 2 } + 11 x y = 20 y - 36 x + 28$$
- Find, in simplest form, \(\frac { \mathrm { d } y } { \mathrm {~d} x }\) in terms of \(x\) and \(y\).
The point \(P ( 4 , k )\), where \(k\) is a constant, lies on \(C\).
Given that \(k < 0\) - find the value of the gradient of \(C\) at \(P\)