(b)
As $p < 0$, therefore $p = - q$, where $q > 0$
$\therefore\ \ \ p^{1/3} = ( - q)^{1/3} = q^{1/3}( - 1)^{1/3}\$
$\ \ \Rightarrow \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ p^{1/3} = - q^{1/3},\ - q^{1/3}\omega,\ - q^{1/3}\omega^{2}$
Let $\alpha = - q^{1/3}$, $\beta =$ $q^{1/3}\omega,\ \$and$\ \ \gamma = - q^{1/3}\omega^{2}$
$\therefore\ \ \ \frac{x\alpha + y\beta + z\gamma}{x\beta + y\gamma + z\alpha} = \frac{x + y\omega + z\omega^{2}}{x\omega + y\omega^{2} + z} = \omega^{2} = \frac{- 1 - i\sqrt{3}}{2}$