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2d
comment How to prove that $k^3+3k^2+2k$ is always divisible by $3$?
It is always divisible by 2, too. So it is always divisible by 6.
Jan
19
comment How to write a definition of less than $<$?
I am not sure if there is a fundamental difference between your answer and my answer but at least you were able to avoid the word "finally".
Jan
19
comment How to write a definition of less than $<$?
@daOnlyBG Maybe it seems to be concise because it uses not much characters. But you first have to define the + binary operator. The answer of Nephente is similar to this answer but avoids + and uses only the successor operator.
Jan
19
comment How to write a definition of less than $<$?
@TheChaz: what is wrong with finally? Is it not possible to use this word here?
Jan
19
comment How to write a definition of less than $<$?
@fleablood you are right (I posted an answer that uses this definition). But your comment and my answer also use $\lt$ in its own definition. So I think the comment of TheChaz is not well stated.
Jan
19
comment How to write a definition of less than $<$?
@TheChaz that can happen in a recursive definition.
Jan
12
comment How to solve instant insanity puzzle with graphs.
@SteveKass I related your answer to the question "how can I find the path from the graph I attached".
Jan
11
comment if the inverse images of all closed balls are closed, is $f$ continuous?
+1, I think this work for all f continous in $(0,\infty)$. So you can use a simpler f like f(x)=x or f(x)=1 in your example.
Jan
7
comment How to solve instant insanity puzzle with graphs.
@SteveKass "Probably not" is probably wrong. Even if it isNP-complete it is possible that it can be solved for input of small size.
Jan
7
comment How to solve instant insanity puzzle with graphs.
Photos are not useful especially if the numbers cannot be read because they are written to small. Put the data in an appropriate format: 3-column list. The first column is the label of the edge (the cube number) the second is the name of the the vertex of the edge with the smaller number (color) and the third column is the other vertex of the edge. But don't add a photo of the list to the post but add it as code (each line is preceded by four whitespace) so that one can copy and paste the data.
Jan
7
comment How to find out the number of ways to solve Instant Insanity
In Donald Knuth's paper Estimating the Efficiency of Backtrack Programs you can find an explanation.
Jan
5
comment Prove that if Triangles ABC = DEF in a metric geometry, then line AB contains exactly two of the points D, E, and F.
"Clearly $\overleftrightarrow{AB}$ cannot intersect any other side at any other point." Any other side of $\bigtriangleup ABC$ or of $\bigtriangleup DEF$ ?
Jan
4
comment Prove that if Triangles ABC = DEF in a metric geometry, then line AB contains exactly two of the points D, E, and F.
definitions can be found here: math.furman.edu/~dcs/courses/math36/assignments.html
Jan
1
comment Shortest distance to a straight line
@copper: If it is the same why did you add this "Alternative" paragraph to your post afterwards?
Dec
16
comment Go from A to D in three equal steps
@Michael: I didn't check this. But the OP shows that there are triples $(a,d,e)$ where at least one solution exists.
Dec
16
comment Go from A to D in three equal steps
for me it is ok if you edit your question in such a way that it does not invalidate my answer, e.g. you can add, that you prefer a geometric proof.
Dec
6
comment What does this ∩ symbol mean in terms of geometry
I rolled back the last edit to make the drawing visible again
Dec
6
comment What does this ∩ symbol mean in terms of geometry
So what means (AB || CD) ∩ CK ?
Dec
1
comment How to handle this curve?
this is your 7th post. you should start to write you formulas in LaTeX
Nov
26
comment Expressing Sets as Regular Expressions
@blues5938 I think more important than thinking about "accurracy" is to think how prove that a regular expression exactly represent a given set of strings , e.g. your setof strings defined by 1. or your set of string given by 2.