3 The equation \(x ^ { 2 } + p x + q = 0\), where \(p\) and \(q\) are constants, has roots - 3 and 5 .
- Find the values of \(p\) and \(q\).
- Using these values of \(p\) and \(q\), find the value of the constant \(r\) for which the equation \(x ^ { 2 } + p x + q + r = 0\) has equal roots.