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Apr
3
comment If $a>0,b>0$ show that exists $x,y\in \mathbb{I}$ near to $a,b$ such that $x^y\in \mathbb{Q}$
Thanks! On the other hand, the function $f$ is not helpful?
Apr
3
comment If $a>0,b>0$ show that exists $x,y\in \mathbb{I}$ near to $a,b$ such that $x^y\in \mathbb{Q}$
@Andres Caicedo, I suppose. The question is not clear, but should be $|x-a|<\varepsilon$ and $|y-b|<\varepsilon$.
Apr
3
asked If $a>0,b>0$ show that exists $x,y\in \mathbb{I}$ near to $a,b$ such that $x^y\in \mathbb{Q}$
Mar
26
awarded  Tumbleweed
Mar
19
accepted Why the spectral theorem is named “spectral theorem”?
Mar
19
revised Finding the points of a horizontal tangent
Just math texts edits
Mar
19
suggested suggested edit on Finding the points of a horizontal tangent
Mar
19
asked Using the inverse function theorem to show that there is a “projection”
Mar
15
accepted Union of topologies
Mar
11
accepted Rank Theorem question
Mar
10
asked Rank Theorem question
Mar
6
accepted A model for the spruce budworm population
Mar
5
asked A model for the spruce budworm population
Feb
27
accepted Chain rule for second derivative
Feb
25
awarded  Notable Question
Feb
24
comment Chain rule for second derivative
@Steven Gubkin, thanks, so $D^2g(f(x_0))$ is also a bilinear map $\mathbb{R}^m\times \mathbb{R}^m\to \mathbb{R}^p$ right? How is that $Dg(f(x_0))D^2f(x_0)(x,y)$ makes sense? Because $Dg(f(x_0))$ is a linear map $\mathbb{R}^n\to \mathbb{R}^p$ and $D^2f:\mathbb{R}^n\times \mathbb{R}^n\to \mathbb{R}^m$
Feb
24
comment Chain rule for second derivative
Ok, I was thinking $Df(x_0)$ like a constant, I mean the derivative evaluated in a point. Then I can get the conclusion only making the product $Df(x_0)(x,y)$, right? Thanks.
Feb
24
asked Chain rule for second derivative
Feb
12
awarded  Popular Question
Dec
11
comment Is something wrong in this proof?
Well, actually this was an exercise and response in a test. It said nothing about the center. Now, do you mean $\limsup\sqrt[n]{|25|}$=1?