If $\;(x+iy)^{\large\frac{1}{3}}= a+ib\;$ where $\;x\;,y\;,a\;,b \in R\;$ show that $\; \large\frac{x}{a} - \large\frac{y}{b} = -2 (a^{2} + b^{2})$

Question

$(a)\;-2(a^{2}+b^{2})\qquad(b)\;2(a^{2}-b^{2})\qquad(c)\;a^{2}+b^{2}\qquad(d)\;2(b^{2}-a^{2})$