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I have a big problem in solving such question:

Let [tex]W(z) = 1 + z + az^n[/tex], where [tex]a[/tex] is complex and [tex]n[/tex] is natural and greater than 1. Show that [tex]W(z)[/tex] has a root that satisfies [tex]|z_k| <=2 [/tex].

I have no ideas how to solve it. I thought about integrating W and showing that it's roots create a circle with radius equal to 2, but it completely didnt work. I would appreciate if someone could give me a clue, as I really can't see any way of solving this one.

rahl