$$A^{p}+B^{p}=C^{p}$$
$B^{p}$$=$$C^{p}$$-$$A^{p}$
$\boldsymbol{a}$$=$$\boldsymbol{C}$$-$$\boldsymbol{A}$
$\boldsymbol{A}$$=$$\boldsymbol{C}$$-$$\boldsymbol{a}$
$$B^{3} = \boldsymbol{a} \left( 3C^{2} -3 \boldsymbol{a} \boldsymbol{C} + a^{2} \right) $$
$$
C^{2}
- \boldsymbol{a} \boldsymbol{C} + \frac{ a^{3} - B^{3} }{3a} = 0$$
$$
\left( \boldsymbol{C}- \frac{1}{2} \boldsymbol{a} \right)^2
+ \frac{ a^{3}-4 B^{3} }{12a} =0$$
$$
\boldsymbol{C}
= \frac{1}{2} \boldsymbol{a} \pm \sqrt\frac{ a^{3}-4 B^{3} }{12a} $$
$$a^{3}-4 B^{3} \lt0 $$