5,935 reputation
31752
bio website ophirgame.com
location United States
age 72
visits member for 3 years, 9 months
seen Dec 14 at 23:13

(update) - My board game was funded on Kickstarter last summer (~$28500)!


I hereby commit to contributing to this site without any rudeness, sarcasm, accusation, or any other unloving speech. (In contrast to The Chaz 1.0)


Dec
10
comment What does this summation notation denote?
Well it's explained right there in the wikipedia page! The "sum" is really more like a successive adding, then subtracting, then adding, then...
Dec
10
comment Evaluating $\frac{d}{dx}\int_{7-2x}^3 \frac{u^3}{1+u^2}du$
I'd switch the limits and (thereby) the sign...
Dec
10
comment What is the difference between $\{1, 2\}\cup\{3\}$ and $\{1, 2, 3\}$?
Right, and we "can" say $1=5$ or omit the differential in an integral, but we'd better keep it conventional for the elementary stuff.
Dec
10
comment What is the difference between $\{1, 2\}\cup\{3\}$ and $\{1, 2, 3\}$?
0 is certainly not the appropriate symbol
Dec
3
comment Suppose a, b, n ∈ N. Use the Euclidean algorithm to prove that gcd(na, nb) = n gcd(a, b)
You didn't calculate (or mention) gcd(na, nb) at all...
Dec
3
comment How can I prove $\sqrt{(111…)+(55…)^2}=5…6$
Square both sides and subtract? If the downvoter can't see that, I guess we're just going to have some downvotes.
Dec
3
comment Explain why $|x^2-x|$ is not differentiable at $x=1$
I wouldn't say we "take off" the absolute value; we evaluate it. For the right-hand limit, the argument of the absolute value is positive (so yes, the | | goes away, in a sense). For the left-hand limit, the argument is negative, so we negate it when evaluating the absolute value.
Dec
3
comment Prove the following properties of binary relations
What do you have for the first one? Are you showing set equality by containment in each direction?
Dec
3
comment Proof: Characterize m
(I mean stylistically - is it appropriate to demonstrate that it holds in two cases, and that it doesn't hold in the other three?)
Dec
3
comment Proof: Characterize m
Would it be sufficient to say that the statement holds, "iff m == a, b" and then just show ==> by inspection of a, b (which we know, but I'm being coy about), and then showing <== by inspection of the other three elements?
Dec
2
comment Calculation of all positive integer $x$ for which $\displaystyle \lfloor \log_{2}(x) \rfloor = \lfloor \log_{3}(x) \rfloor \;,$
Most of my questions/answers on here were from an iPad as well, so I understand the struggle! A workaround is to click "edit" on the question, then copy+paste relevant code. A litte "\log_{2}" would go a long way in your answer (wrapped in dollar signs, of course).
Dec
2
comment Calculation of all positive integer $x$ for which $\displaystyle \lfloor \log_{2}(x) \rfloor = \lfloor \log_{3}(x) \rfloor \;,$
You can/should right-click a mathematical expression to see its LaTex format: [Show math as] --> [Tex commands]. An example from this question is: \displaystyle \lfloor \log_{2}(x) \rfloor = \lfloor \log_{3}(x) \rfloor \;
Dec
2
comment Proof: Characterize m
Yes. What happens when you square $0,1,2,3,4$, mod 5?
Sep
30
awarded  Explainer
Aug
2
awarded  Nice Question
Jul
29
comment Simplify $S=\sum_{i=0}^{k}a_i (2n)^{2i+1}$
What have you tried? etc.
Jul
28
comment Surjective function - proving
Surjective means that for any point b in the codomain, you can find a point a in the domain such that $$f(a) = b$$. If you can't "get to" certain (positive values), then the function is not surjective.
Jul
27
awarded  Popular Question
Jul
2
awarded  Curious
Jun
5
awarded  Revival