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 15h comment Does there exist the function $f^2(x)\ge f(x+y)\left(f(x)+y \right)$ how do you get the first inequality? Apr 5 comment Is a continuous function plus a discontinuous function discontinuous? If $f+g$ is continuous where $f$ is continuous, then $(f+g)-f=g$ is continuous. Mar 25 comment For differentiable functions $f,g$, $\nabla f(x)=g(x)x$. Then $f$ is constant on S. g(x) is a scalar. Sep 13 comment What does the sum notation $\sum\limits_{j=n}^\infty a_j$ mean? Following an expression by a comma and then "$n\in\mathbb N$" is the same as writing "where $n$ is a natural number". It does not denote a sequence. Aug 14 comment Which of the following are bijections? Just for fun: If you think $x^5$ looks flat near 0, check out what $e^{-1/x^2}$ looks like near 0. I remember graphing that function in my undergrad days and being astonished by how flat it looks! Aug 10 comment Proving $\mathbb{R}^2 \rightarrow \mathbb{R}^2$ function is bijective. See the third question in the list of related questions: math.stackexchange.com/questions/467322/… Jul 29 awarded Yearling Jul 26 comment Why the determinant of a matrix with the sum of each row's elements equal 0 is 0? I don't understand how this answers the question. You seem to be interpreting OP's question to mean that there is a row of all 0s. Jul 11 comment Balancing the weights of the vertices of a graph by averaging along the edges. Are any nontrivial results known? Is it possible for the complete graph on 5 vertices? Where can I read about the 8-cycle problem? Jul 11 comment Balancing the weights of the vertices of a graph by averaging along the edges. I did a breadth-first search in Python. Starting with 0 on the vertices in the triangle and 1 on the remaining vertex, then an equillibrium is not reached within 26 moves (at which point 8 million inequivalent configurations had been reached). Worth noting: starting from the above configuration, the vertex which started at 1 will not remain as the node with the maximum value forever, which is what I based my proof strategies on. Jul 7 comment Balancing the weights of the vertices of a graph by averaging along the edges. Are there any examples of graphs with at least 3 vertices where it's known to be possible? Jun 28 comment Can this expression be made true ? 2 _ _ _ _ = 2015 If a unary + symbol is allowed, then you can get up to $2\times+99=198$. Jun 13 revised Images of a familiar object in $\mathbb{R}^3$ mapped to $\mathbb{R}^2$ by Cantor/Peano/Hilbert added 297 characters in body Jun 13 revised Images of a familiar object in $\mathbb{R}^3$ mapped to $\mathbb{R}^2$ by Cantor/Peano/Hilbert added 691 characters in body Jun 13 revised Images of a familiar object in $\mathbb{R}^3$ mapped to $\mathbb{R}^2$ by Cantor/Peano/Hilbert deleted 10 characters in body Jun 13 answered Images of a familiar object in $\mathbb{R}^3$ mapped to $\mathbb{R}^2$ by Cantor/Peano/Hilbert May 11 comment ZELDA Guardian Puzzle Part II - Shortest Path (Unsolved for new rules) Well this post doesn't contain a question and doesn't make sense unless you read the linked post. I'm guessing the votes to close are due to that. If the text from the previous question is edited in, I think all objections would disappear. May 10 reviewed Approve Uniform convergence and maximum of an absolute difference May 4 comment Brouwer's fixed point continuous function For $C$, you can see math.stackexchange.com/questions/478517/… . May 4 comment Brouwer's fixed point continuous function For $A$, just map $(x_1,x_2)$ to $x_1$. Call the map $h:A\to [-1,1]$. You should be able to prove that if $f:A\to A$ has a fixed point, then $h\circ f\circ h^{-1}:[-1,1]\to[-1,1]$ has a fixed point, and vice versa.