4meonly wrote:I still do not understand why we should not make 16^2 from f(16). Why we make two second powers of -2 but do not do it with 16?
Please, help to understand! Thank you!
You certainly
can say that f(16) = f(256), but it's just not useful to do here. What we do know here is that f(x) is always equal to f(x^2). So, for example,
f(2) = f(4) = f(16) = f(256) = f(65536) = ...
and
f(3) = f(9) = f(81) = f(6561) = ...
So any of the following would be equal to zero:
f(4) - f(2)
f(256) - f(2)
f(4) - f(65536)
f(81) - f(6561)
etc
We replaced f(-2) with f(4), and then with f(16), above in order to show that f(-2) and f(16) were equal, and once we'd done that, we stopped working - the job was done. Still, we certainly could have replaced f(16) with f(256), for example; it just wasn't necessary or helpful to do so.
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