7. The curve \(C\) has equation \(y = \mathrm { f } ( x ) , x > 0\), where
$$\mathrm { f } ^ { \prime } ( x ) = 30 + \frac { 6 - 5 x ^ { 2 } } { \sqrt { x } }$$
Given that the point \(P ( 4 , - 8 )\) lies on \(C\),
- find the equation of the tangent to \(C\) at \(P\), giving your answer in the form \(y = m x + c\), where \(m\) and \(c\) are constants.
- Find \(\mathrm { f } ( x )\), giving each term in its simplest form.