Whats the best way to show this?

they're both exactly the same, but I would say b) is easier to work with and gets your point across more clearly.

 

I like (a), but that's only because I almost never see it, and I didn't know how to do it in latex until just now.

 

To use a calculator for a certain value of x, 1. leads to 2., so use 2. without worrying about root symbols.

 

yeah, I vote for b), too. More general and lends itself for easy inclusion into equations, polynomials, etc.