6 The variables \(x\) and \(y\) satisfy the differential equation
$$\frac { \mathrm { d } ^ { 2 } y } { \mathrm {~d} x ^ { 2 } } + 16 y = 8 \cos 4 x$$
- Find the complementary function of the differential equation.
- Given that there is a particular integral of the form \(y = p x \sin 4 x\), where \(p\) is a constant, find the general solution of the equation.
- Find the solution of the equation for which \(y = 2\) and \(\frac { \mathrm { d } y } { \mathrm {~d} x } = 0\) when \(x = 0\).