How to impose 'Second Order Approximation'?

How would I impose 'Second Order Approximation' to the system below?

[Nkenna Amadi]

hey can i know where you got this question from ?

Answer 1

[Star Strider]

The only possibility that comes to mind in my experience is to take it back to the time domain and calculate a second-order Taylor series representation of it. (That’s usually done for nonlinear systems in order to linearise them, but yours seems to me to be linear.)