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Special functions, orthogonal polynomials, harmonic analysis, ordinary differential equations (ODE's), differential relations, calculus of variations, approximations, expansions, asymptotics.

-6 votes
1 answer
432 views

On the extension of a limit [closed]

We know that $\lim_{p\rightarrow\infty}\left\Vert \left(x_{1},\cdots,x_{n}\right)\right\Vert _{p}=\max\left\{ \left|x_{1}\right|,\cdots,\left|x_{n}\right|\right\} =:\left\Vert x\right\Vert _{\infty}$ …
user4606's user avatar
1 vote
2 answers
395 views

Are there always nontrivial real solutions to $A_1 x^5 + B_1 y^5 + C_1 z^5 = 0$ and $A_2 x +...

Firstly, are there always nontrivial real solutions to the sysytem of equations, $A_{1}x^{5}+B_{1}y^{5}+C_{1}z^{5}=0$ and $A_{2}x+B_{2}y+C_{2}z=0$, for real numbers $A_{1}$, $B_{1}$, $C_{1}$, $A_{2}$, …
user4606's user avatar
0 votes
1 answer
357 views

Questions on supremum

Is it true that $$\sup_{x\in\mathbb{R}}\frac{\left|\left(1+s\right)+tx\right|+\left|\left(1+t\right)x+s\right|}{1+\left|x\right|+\left|s+tx\right|}\geq1$$ for all $s,t\in\mathbb{R}$? Is it also true t …
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-3 votes
2 answers
260 views

On \ell_3 norm in R^2

Let $v,w\in\mathbb{R}^{2}$ and $v\perp w$. Is it true that $\left\Vert v\right\Vert _{3}\leq\left\Vert v+w\right\Vert _{3}$, in which $\left\Vert \left(x,y\right)\right\Vert _{3}:=\sqrt[3]{\left|x\rig …
user4606's user avatar