6 A curve is defined by the equation \(x ^ { 2 } y + y ^ { 3 } = 2 x + 1\).
- Find the gradient of the curve at the point \(( 2,1 )\).
- Show that the \(x\)-coordinate of any stationary point on this curve satisfies the equation
$$\frac { 1 } { x ^ { 3 } } = x + 1$$
(4 marks)