163 reputation
15
bio website roryokane.com
location
age 23
visits member for 2 years, 6 months
seen Nov 7 at 21:25

Oct
20
awarded  Necromancer
Dec
4
comment $x$, $y$, $x+y$ and $x-y$ are prime numbers. What is their sum?
I didn’t understand this question until I looked at the answers below. I thought the answer was “$3x+y$, obviously”. But now I see that you are looking for an actual number as an answer. The answers below show that there is only one set of values for $x$ and $y$ that makes the four integers positive and prime, so the actual work of the question is “what are the (only possible) values of $x$ and $y$?”. You’re saying you answered that question by brute-force guessing, but you want to know how to answer it with mathematical reasoning.
Nov
14
revised How could we solve $x$, in $|x+1|-|1-x|=2$?
improve wording of description of some steps
Nov
14
comment How could we solve $x$, in $|x+1|-|1-x|=2$?
I can confirm Bill Dubuque’s comment. I continued working through this approach and ended up with $0=0$.
Nov
14
answered How could we solve $x$, in $|x+1|-|1-x|=2$?
Nov
14
revised How could we solve $x$, in $|x+1|-|1-x|=2$?
fixed spelling/grammar/typography, improved wording, linked to another relevant plot, explained “CW”
Nov
14
revised How could we solve $x$, in $|x+1|-|1-x|=2$?
fixed typo in final answer “[1,∞[”, wrote out steps of third case like the first and second cases
Nov
14
suggested approved edit on How could we solve $x$, in $|x+1|-|1-x|=2$?
Nov
14
comment Maximum of the difference
(Though I don’t understand this explanation, its general solution at the end gives solutions for $f_1$ through $f_{10}$ that match the solutions given by my brute-force solver. So that general solution is probably correct.)
Nov
14
comment Maximum of the difference
… I think your explanation would be clearer if it were written with different notation. You could use function notation (change $x_k$ to $d(x, k)$), or you could expand $x_k$ into $(n-k)$ if your new notation is just for conciseness.
Nov
14
comment Maximum of the difference
I’m confused by your notation – I think you’ve overloading subscript too much. Inside your definition of $f$, I thought that the $x_1$, $x_2$, etc. were just numbered placholders. But in the first paragraph, you seem to define a new meaning of subscript. When you define $x_k$, are you defining a new notation, or are you claiming that $x_1$, etc. in your definition of $f$ always follow that pattern? And does your definition of $x_k$ apply to terms like “$n_4$”, or does the first variable have to be $x$? …
Nov
13
revised Maximum of the difference
corrected Big O of maximumValuesForSetsUpTo – O(n*n!) = O(n^2*(n-1)!) = O((n-1)!) = O(n!)
Nov
13
answered Maximum of the difference
Nov
13
comment How to convince a layman that the $\pi = 4$ proof is wrong?
Further reading: Euclidean distance and taxicab distance.
Nov
13
awarded  Excavator
Nov
13
comment Is value of $\pi = 4$?
Wikipedia links explaining some concepts mentioned here: calculus and (numerical) analysis (classes). Riemann sum. limsup (limit superior).
Nov
13
revised Is value of $\pi = 4$?
replaced \sim(ilar order of magnitude) with \approx(imately equal); improved spelling, grammar, typography
Nov
13
suggested approved edit on Is value of $\pi = 4$?
Nov
13
comment Why is $\sqrt{8}/2$ equal to $\sqrt{2}$?
To clarify what the edit to the question was: the question originally asked, incorrectly, why $\sqrt{8}/2$ is equal to $\sqrt{4}$. Now it correctly asks why $\sqrt{8}/2$ is equal to $\sqrt{2}$.
Nov
13
awarded  Editor