Simplify the following:

$\Big(x - \dfrac{3}{x}\Big)\Big(x^2 + 3 + \dfrac{9}{x^2}\Big)$

We know that (a - b)(a² + ab + b²) = a³ - b³

∴ Given Expression = $\Big(x - \dfrac{3}{x}\Big)\Big(x^2 + 3 + \dfrac{9}{x^2}\Big)$

$= x^3 - \Big(\dfrac{3}{x}\Big)^3 \\[1em] = x^3 - \dfrac{27}{x^3}$