Use an algebraic method to find the square roots of the complex number \(16 + 30 \mathrm { i }\).
Use your answers to part (i) to solve the equation \(z ^ { 2 } - 2 z - ( 15 + 30 \mathrm { i } ) = 0\), giving your answers in the form \(x + \mathrm { i } y\).