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for questions involving inequalities, upper and lower bounds.

1 vote

Find the best constant to this bounded inequality

@T.Amdeberhan - I think that the constant $\frac{5}{3}$ is optimal. Take $x_1=1/4^{m}$, $x_2=1/4^{m-1}$,$\dots$ ,$x_m=1/4$, $x_{m+1}=1$, $x_{m+2}=1/4$, $\dots$, $x_{2m}=1/4^{m-1}$, $x_{2m+1}=1/4^m$, t …
Robert Z's user avatar
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4 votes
Accepted

Find the best constant to this bounded inequality

These are some thoughts concerning the Question. We have that \begin{align*} &S_n(3)=\sum_{1\leq i\leq n}x_i^3< \sum_{i\geq 1}4^{-i}=1/3,\\ &S_n(1,2)=\sum_{1\leq i<j\leq n}x_i x_j^2< \sum_{1\leq i<j}4 …
Robert Z's user avatar
  • 343
8 votes
1 answer
617 views

Inequality for Stirling numbers of the second kind

I stumbled upon the following inequality which, I believe, is true. I was able to prove it for small k, but I have no proof for the general case. Any help is welcome. Let $n\geq k\geq 1$ then $$\left …
Robert Z's user avatar
  • 343
2 votes
1 answer
333 views

Given $P\in \mathbb{Z}[x]$ there is a nonzero $Q\in \mathbb{Z}[x]$ such that $H(PQ)\leq M(P)$

I am looking for a proof (or references) for the following result: If $P\in \mathbb{Z}[x]$ then there exists a nonzero polynomial $Q\in \mathbb{Z}[x]$ such that $$H(PQ)\leq M(P)$$ where $H(R)=\max\{| …
Robert Z's user avatar
  • 343