# Jorge Fernández

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bio website location Mexico City age member for 2 years, 6 months seen 7 mins ago profile views 1,976

Hello, I am a freshman at The National Autonomous University of Mexico (UNAM).

My interests are contest problems,elementary number theory, combinatorics, graph theory, linear algebra, group theory, abstract algebra and I have been meaning to learn category theory and matroids.

# 2,904 Actions

 18h comment $x^2-y^2=2s$, s cannot be an odd integer Oh, this solution is much better than mine. +1 18h answered $x^2-y^2=2s$, s cannot be an odd integer 18h revised $x^2-y^2=2s$, s cannot be an odd integer added 2 characters in body; edited title 18h comment Triangle-free graph with 5 vertices with $5$ vertices. If there is no restiction on the number of vertices you can find a bipartite graph with as many edges as desired. 18h comment Triangle-free graph with 5 vertices Oh, we thought of the same thing, they say poor minds think alike. 18h answered Triangle-free graph with 5 vertices 22h revised Number of ways to arrange items added 116 characters in body 22h comment Number of ways to arrange items $f_k(n)$ are the same as the stirling numbers of the first kind 22h revised Number of ways to arrange items deleted 16 characters in body 23h revised Number of ways to arrange items added 20 characters in body 23h revised Number of ways to arrange items added 2 characters in body 23h answered Intersect of Stabilizers is a Normal Group 23h answered Number of ways to arrange items 1d awarded Custodian 1d comment Minimize total cost of one kilometer Something is wrong, the cost per hour should always be over $100$. are you sure the cost per hour is $25$ when the speed is $25$? 1d answered Set with distinct subset sums 1d comment How to solve this kind of problem? I solved it using integers, I think it becomes harder if we can only use naturals. 1d revised How to solve this kind of problem? added 267 characters in body 1d comment Check if Sequence is Graphic: 8, 8, 7, 7, 6, 6, 4, 3, 2, 1, 1, 1 I mean, you should count the degrees in the graph to make sure, but I can't find more conclusive evidence it is graphic 1d comment Check if Sequence is Graphic: 8, 8, 7, 7, 6, 6, 4, 3, 2, 1, 1, 1 Well, I counted the degrees in the graph in the solution and it is correct, are you sure you copied the sequence correctly?