3. Given that 2 and \(1 - 5 \mathrm { i }\) are roots of the equation
$$x ^ { 3 } + p x ^ { 2 } + 30 x + q = 0 , \quad p , q \in \mathbb { R }$$
- write down the third root of the equation.
- Find the value of \(p\) and the value of \(q\).
- Show the three roots of this equation on a single Argand diagram.