Hi maths helpers,

I need some help with this one

I understand the question and still didn't get the answer. I looked at the worked solution.

I found this

What I want to know is why did the author chose to do:

$\displaystyle \frac{\frac{1}{1-x} }{\frac{1}{1-x^2}} = \frac{5}{4} $

Please can someone explain

thank you