Jorge Fernández

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bio website location Monkey Island, OK age member for 2 years, 3 months seen 40 mins ago profile views 1,593

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.

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 23h answered Total probability 23h answered Special Arrangement 1d comment Is there such a thing as the Fundamental Theorem of ZFC? I don't think most people here are familiar with the game of ZFC. Could you state what the rules are please? 1d comment Is this calculus proof I came up with sound? I made a small mistake with the indexes, I think it is ok now. Am I right the proof is fine now as is? Thank you David. 1d revised Is this calculus proof I came up with sound? added 19 characters in body 1d comment Is this calculus proof I came up with sound? I should be more precise? I'm no expert, but do intervals like that make sense on complex numbers? 1d asked Is this calculus proof I came up with sound? 1d revised What is the smallest natural number n? deleted 36 characters in body 1d awarded Popular Question Sep18 comment Probability: Distinguishable vs Indistinguishable oh, I should have written $5/9$ since we want the complement of what I had, it is the same as the sum you wrote, only computed in a slightly different way Sep18 comment Probability: Distinguishable vs Indistinguishable I don't even see why the method for selecting the balls matters. Wouldn't it be the same to say: pick two distinct balls, what's the probability they are of the same color, since there are $9\cdot8/2$ ways to select 2 distinct balls and $5\cdot4/2+4*3/2$ ways to select of the same color we get the probability is $16/36=4/9$ Sep18 revised Truth table and the meaning of $\oplus$ in propositional logic deleted 24 characters in body Sep18 answered Truth table and the meaning of $\oplus$ in propositional logic Sep17 asked placing chess knights in a numbered chessboard. Sep16 answered The larger of two supplementary angles exceeds 7 times the smaller by 4 degrees. Find the measure of the angle. Sep16 comment Can a game with negative expectation still have a positive utility? yes, the reason why economists sometimes want their utilities to be concave down is because this means they are "against risk", and at least in the algebra of words "against risk" would imply players would never want to play if the expected value was non-positive. Sep16 answered Can a game with negative expectation still have a positive utility? Sep13 accepted Calculating $\sum_{k=1}^nk(k!)$ combinatorially Sep13 comment Calculating $\sum_{k=1}^nk(k!)$ combinatorially I meant that each term was going to be $(k+1)!-k!$ Sep13 comment Distribute n identical objects into r distinct groups It foesn't, if two overlap it means that there are no stars between those bars. If you want to ensure at least 1 for each category just take away 1 star for each category and do the same. so the formula would be $\binom{k-1}{n-1}$