I have a question in my book as follow:

Use the base 2 test on 511 and 509

(base 2 test is n does not satisfy then it is composite)

For the first part I think I am good:

Noting that so

and is not

However for the second part I get a bit confused:

so

But I am a bot confused as to where to go next.

Thanks for any help

(oh and anybody knows the Latex symbol for not equivalent that would be great)