How to factorise that to the simplest form

[delicate ibex]

@meager creek, what is written before $a^{-3}$? Can't understand the handwriting.

Anyways, whatever that thing is, here's a tip:

$$x^{-n} = \frac{1}{x^n}$$

[craggy ember]

@delicate ibex

[delicate ibex]

that's because:

$$x^{m} : x^{m + n} = x^{m - \left(m + n\right)} = x^{-n}$$

$x^m = x * x * x * ... * x$ } m times

$x^{m + n} = x * x * x * ... * x$ } m + n times
$$x^{m} : x^{m + n} = 1 : x^{n} = \frac{1}{x^n}$$

[craggy ember]

@delicate ibex

[primal dock]

\underbrace can be used