Old John
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 Mar14 awarded Nice Answer Mar7 comment Complex analysis textbook advise I think you will find that Needham really does concentrate on the most important stuff - for a serious understanding of what matters in complex analysis. Note sure that size is relevant. Mar7 comment Definite Integral of $\sin^4(x)\cos(x).$ What exactly does "them" mean in that comment? Mar7 answered Complex analysis textbook advise Feb26 comment Sum and Divisibility Puzzle The title is very misleading - this has nothing to do with unique factorisation. Feb26 revised Sum and Divisibility Puzzle Retagged Feb24 answered Integration and measure theories, a reference list Feb24 comment if $x^3-x\in\mathbb{Z}$ and $x^4-x\in\mathbb{Z}$ for some $x\in\mathbb{R}$, then $x\in\mathbb{Z}$. Hmm - you seem to have changed the roles of $a$ and $b$ ... and your statement (2) isn't actually a statement? Feb24 comment if $x^3-x\in\mathbb{Z}$ and $x^4-x\in\mathbb{Z}$ for some $x\in\mathbb{R}$, then $x\in\mathbb{Z}$. Not sure, but I am a bit baffled by your first 2 lines. From your assumptions, it follows that $x+a = x^3$, but you seem to be claiming that $x+a = x.x^3$ - how did you get that? Feb24 awarded Enlightened Feb24 awarded Nice Answer Feb20 reviewed Approve Curious representation of primes Feb20 comment In the Collatz function, why does $2^k-1$ reach $3^k-1$ after $2k$ steps, and could it be used to find divergent trajectories? Assuming anyone still believes that he really did have such a proof! Feb20 comment In the Collatz function, why does $2^k-1$ reach $3^k-1$ after $2k$ steps, and could it be used to find divergent trajectories? Since some seriously powerful problem-solvers have attacked this problem (e.g. Erdős), I think we can assume that all elementary approaches such as this have been tried and they have clearly failed. Feb13 comment Finding the mod of a difference of large powers It doesn't help, because both are clearly not divisible by 35. Just find if the two powers have the same residue mod 35 Feb13 revised Product of the binary quadratic form $Q(x,y)=2x^2+2xy+3y^3$ added 3 characters in body Feb13 revised Product of the binary quadratic form $Q(x,y)=2x^2+2xy+3y^3$ edited body Feb10 comment Is there formula for the volume of a hexahedron? Still not sure what this is: what if your last four points do not lie in a plane? Feb10 comment Is there formula for the volume of a hexahedron? Even if you really mean a plane, what exactly do you mean by a space "bounded by" 4 points and a plane? You need to explain much more precisely what you have in mind. Also, two of your "four" points seem to be identical. Jan30 comment $n \mid k^2 \land n+1 \mid l^3 \land n+2 \mid m^4 \to n=?$ Maybe I was just lucky. I certainly didn't try all the possibilities, and couldn't see a simple/precise way to get to the minimum solution quickly.