$\left\{\begin{matrix}I=\frac{x^{3}-1}{afx^{2}}\text{, }&x\neq 0\text{ and }f\neq 0\text{ and }a\neq 0\\I\in \mathrm{R}\text{, }&\left(f=0\text{ or }a=0\right)\text{ and }x=1\end{matrix}\right.$

$\left\{\begin{matrix}a=\frac{x^{3}-1}{Ifx^{2}}\text{, }&x\neq 0\text{ and }f\neq 0\text{ and }I\neq 0\\a\in \mathrm{R}\text{, }&\left(f=0\text{ or }I=0\right)\text{ and }x=1\end{matrix}\right.$