Inequalities for the polar derivative of a polynomial with $S$-fold zeros at the origin
نویسندگان
چکیده مقاله:
Let $p(z)$ be a polynomial of degree $n$ and for a complex number $alpha$, let $D_{alpha}p(z)=np(z)+(alpha-z)p'(z)$ denote the polar derivative of the polynomial p(z) with respect to $alpha$. Dewan et al proved that if $p(z)$ has all its zeros in $|z| leq k, (kleq 1),$ with $s$-fold zeros at the origin then for every $alphainmathbb{C}$ with $|alpha|geq k$, begin{align*} max_{|z|=1}|D_{alpha}p(z)|geq frac{(n+sk)(|alpha|-k)}{1+k}max_{|z|=1}|p(z)|. end{align*} In this paper, we obtain a refinement of above inequality. Also as an application of our result, we extend some inequalities for polar derivative of a polynomial of degree $n$ which does not vanish in $|z|< k$, where $kgeq 1$, except $s$-fold zeros at the origin.
منابع مشابه
extensions of some polynomial inequalities to the polar derivative
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عنوان ژورنال
دوره 43 شماره 7
صفحات 2153- 2167
تاریخ انتشار 2017-12-30
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