(a)[2]
Write $4x^2 - 24x + p$ in the form $a(x + b)^2 + c$, with $a$ and $b$ integers and $c$ expressed using the constant $p$.
(b)[1]
Hence, or by another method, determine the set of values of $p$ for which the equation $4x^2 - 24x + p = 0$ has no real roots.