Factorize:

$216 x^{3}+\frac{1}{125}=(6 x)^{3}+\left(\frac{1}{5}\right)^{3}$

$=\left(6 x+\frac{1}{5}\right)\left[(6 x)^{2}-6 x \times \frac{1}{5}+\left(\frac{1}{5}\right)^{2}\right]$

$=\left(6 x+\frac{1}{5}\right)\left(36 x^{2}-\frac{6 x}{5}+\frac{1}{25}\right)$