(a) Find the two square roots of the complex number \(-3 + 4i\), giving your answers in the form \(x + iy\), where \(x\) and \(y\) are real.

(b) The complex number \(z\) is given by

\(z = \frac{-1 + 3i}{2 + i}.\)

1. Express \(z\) in the form \(x + iy\), where \(x\) and \(y\) are real.
2. Show on a sketch of an Argand diagram, with origin \(O\), the points \(A\), \(B\) and \(C\) representing the complex numbers \(-1 + 3i\), \(2 + i\) and \(z\) respectively.
3. State an equation relating the lengths \(OA\), \(OB\) and \(OC\).