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11h
comment Isn't $ n(n-1)(n-2)…(n-m+1) $ a factorial already?
@BrianM.Scott Man, that's what I tried to tell the guy this morning when I forgot to get out of reverse and backed into his Volkswagon...
14h
answered Isn't $ n(n-1)(n-2)…(n-m+1) $ a factorial already?
15h
answered How do I prove that if $p$ is prime then $p$ divides $2^{p}-2$?
20h
answered Why do we need primitive roots?
2d
comment stone weierstrass approximation theorem for simple functions: does it exist?
@zorank I see, so you have a particular algebra (at least hypothetically) and want to check if it can approximate simple functions. In my second paragraph I was addressing the question "is there any algebra which can approximate simple functions", hence why I said that since simple functions are themselves an algebra, the question is trivial. But that doesn't really help in your case.
2d
answered stone weierstrass approximation theorem for simple functions: does it exist?
2d
accepted The series $2+3x+5x^2+7x^3+11x^4+…$
2d
reviewed Reject Studying math all day and really young
2d
reviewed Reject If $|B\times A| = 15$ ,evaluate: $|A\cap B|$
Jan
27
comment Is there a notation for being “a finite subset of”?
@Lehs What structure are you working in in which $\infty<\infty$ ?
Jan
27
answered My proof that there are primitive roots modulo $p^2$
Jan
27
revised the value of $e$ and the method of getting it
edited tags
Jan
26
asked My proof that there are primitive roots modulo $p^2$
Jan
26
comment Pyramid inside a rectangular tank
Please use more descriptive titles - "Need help with math" could describe any question on this site!
Jan
26
revised Pyramid inside a rectangular tank
edited tags; edited title
Jan
25
comment Could someone take a crack at this number theory problem?
I've never heard the term "complete residue system modulo $m$", that's a very convoluted way of saying "the set $\mathbb Z/m\mathbb Z$"... So you want to show that multiplication by $a$ permutes that set, in other words, that it's a bijection.
Jan
25
comment Progressive Matrices Puzzle
Each table is a permutation of the preceding table, however there is no single permutation $p$ such that each table is $p$ of the preceding table.
Jan
25
comment Selfy number couldn't exist?
To clarify your definition for other users: let $s(x)$ denote the sum of the digits of $x$, let $l(x)$ denote the number of digits of $x$. Many numbers $n$ can be expressed as $n=x+s(x)$ for some $x$. Perhaps others cannot, but they can be expressed as $n=x+l(x)$ for some $x$. A selfy number is one which can be expressed in neither form.
Jan
24
answered How can we think and/or write rigorously about integration by substitution?
Jan
23
comment What's your favorite proof accessible to a general audience?
Any explanation for $0.999...=1$ that doesn't start with the definition of an infinite series is worthless - worse than that, it's misleading about the nature of mathematics. The fundamental thing to understand about $0.999...=1$ is that it is true by definition, it's not fundamentally true in some cosmic, platonic sense. It is simply that the notation $0.999...$ makes no sense without a definition, and the definition which we happen to use leads to its value being $1$.