7. A curve has equation \(y = \frac { 1 } { 4 } x ^ { 4 } - x ^ { 3 } - 2 x ^ { 2 }\).
i. Find \(\frac { d y } { d x }\).
ii. Hence sketch the gradient function for the curve.
iii. Find the equation of the tangent to the curve \(y = \frac { 1 } { 4 } x ^ { 4 } - x ^ { 3 } - 2 x ^ { 2 }\) at \(x = 4\).