Ewan Delanoy
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 6h revised Rational function between a constant and a third root edited body 6h revised Rational function between a constant and a third root edited body 7h revised Rational function between a constant and a third root added 3 characters in body 7h comment Rational function between a constant and a third root @MXYMXY Clearly the degree of $P$ must equal the degree of $Q$. Otherwise $f$ would either grow too fast for the upper bound or decrease too fast for the lower bound 7h asked Rational function between a constant and a third root 9h revised Optimizing value of discrete harmonic function at a given point added 20 characters in body 9h answered How to prove this result about the interlacing of eigenvalues. Apr 27 comment Find smallest k for which the inequality holds What did you try ? What are your thoughts ? Apr 26 asked Optimizing value of discrete harmonic function at a given point Apr 24 revised Prove that for any $A \neq 0$ there is a matrix $B$ such that $A + B$ and $B$ have no eigenvalues in common. added 414 characters in body Apr 24 answered Prove that for any $A \neq 0$ there is a matrix $B$ such that $A + B$ and $B$ have no eigenvalues in common. Apr 22 accepted Denominator is product of irreducibles with cyclic Galois group Apr 21 comment Estimate the bound of the sum of the roots of $1/x+\ln x=a$ where $a>1$ @Chip This second problem is of no use to me either. Thanks for your feedback Apr 21 comment Description of certain invariant polynomials (not a group action) @user062295 1) Which part of my question is unclear to you ? 2) If you think that there is in fact a group action here, could you describe the group $G$ and the action ? Because I don't see any so far. Apr 20 comment $\det(ABC) = \det(B)\det(AC)$? When $B$ is the identity matrix, for example. Apr 20 comment Estimate the bound of the sum of the roots of $1/x+\ln x=a$ where $a>1$ @Chip Wow! I'm so flattered that you're asking me to solve a question which you think is unworthy of being asked at MSE ... Apr 19 comment Given $U,v,w$ find $u \in U$ that value of $||u-w|| + || v - u||$ will be minimal Sorry, my bad, the situation is a little bit more complicated than I thought, I finally included an answer Apr 19 answered Given $U,v,w$ find $u \in U$ that value of $||u-w|| + || v - u||$ will be minimal Apr 19 comment Given $U,v,w$ find $u \in U$ that value of $||u-w|| + || v - u||$ will be minimal @IlanAizelmanWS You might want to look up the words you don't understand in Google/Wikipedia/whatever, or ask about them here. user1952009 has also added a little bit of additional help for you above Apr 19 comment Given $U,v,w$ find $u \in U$ that value of $||u-w|| + || v - u||$ will be minimal There is a one-line complete answer : By the triangle inequality, $||v-u||+||u-w|| \geq ||v-w||$ with equality iff $u$ is a convex combination of $u$ and $v$. No wonder people like user1592009 are surprised by your question