Camillo ha scritto:@Zero87
Why do you write that for $|z| =1 $ , it is $|g(z)| =|z^7-2z^5-z+1| = 1$ , while it is $|g(z)| <= 5 $ ?.
Mi sono connesso apposta per correggere l'errore - ah sorry - i take access in this forum because i remember that is an error in my proof.
I wrote:
$|g(z)| =|z^7-2z^5-z+1| = 1$
That is an example of my personal stupidity and distraction, but the correct (i suppose) soluction is:
$|g(z)| =|z^7-2z^5-z+1| \le |z^7|+|-2z^5|+|-z|+|1|=5$ for the triangular inequality. But the result is correct (i controlled also on wolphramalpha.com).
Bye
