8 The points \(P\) and \(Q\) lie on the curve with equation
$$2 x ^ { 2 } - 5 x y + y ^ { 2 } + 9 = 0$$
The tangents to the curve at \(P\) and \(Q\) are parallel, each having gradient \(\frac { 3 } { 8 }\).
- Show that the \(x\) - and \(y\)-coordinates of \(P\) and \(Q\) are such that \(x = 2 y\).
- Hence find the coordinates of \(P\) and \(Q\).