Exercise 9.   Suppose that  [Graphics:Images/RoucheTheoremModHome_gr_524.gif]  is analytic and nonzero and  [Graphics:Images/RoucheTheoremModHome_gr_525.gif]   for   [Graphics:Images/RoucheTheoremModHome_gr_526.gif].  

Prove that the function   [Graphics:Images/RoucheTheoremModHome_gr_527.gif]   has  n  zeros inside the unit circle  [Graphics:Images/RoucheTheoremModHome_gr_528.gif].  

Solution 9.

Solution.   Let  [Graphics:../Images/RoucheTheoremModHome_gr_529.gif].   Then for  [Graphics:../Images/RoucheTheoremModHome_gr_530.gif]  we have

          [Graphics:../Images/RoucheTheoremModHome_gr_531.gif]  

Since  [Graphics:../Images/RoucheTheoremModHome_gr_532.gif]  has n zeros in  [Graphics:../Images/RoucheTheoremModHome_gr_533.gif],  then  [Graphics:../Images/RoucheTheoremModHome_gr_534.gif]  has n zeros inside the unit circle  [Graphics:../Images/RoucheTheoremModHome_gr_535.gif],  by Remark 8.5 to Rouché's Theorem.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

This solution is complements of the authors.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

(c) 2008 John H. Mathews, Russell W. Howell