Reputation
6,683
Top tag
Next privilege 10,000 Rep.
Access moderator tools
Badges
4 21 55
Impact
~217k people reached

Jan
16
comment Help understanding what is asked of me
Ducksauce, I'm almost certain it's in your book somewhere. What text are you using? (Or can you upload a scan of your notes?)
Jan
16
comment All matrices which commute with all $2\times 2$ matrices
@USB - for the sake of argument, how do you know that "this answer is correct"?
Jan
15
comment The Sum Of Sets Or Intervals
You're ignoring the context. $A$ and $B$ must be sets where addition ($+$) makes sense. So then the addition on the L.H.S. is really a new type, defined by adding (using the addition of $A,B$) elements of $A,B$.
Jan
15
comment Breaking symmetries
The link in the penultimate paragraph is dead ("inaccessible")...
Jan
14
comment Finding a limit algebraically
Lots of spoon-feeding going on in these answers! And yet nobody took the time to demonstrate the manipulation of the L.H.S...
Jan
12
comment Combinatorics: Prove the number of matches in a Singles Tournament
How is it obvious?
Jan
8
reviewed Approve Why the answer to $\log(x+3)+\log(x+2)\geq \log 12$ different from that of $\log(x^2+5x+6)\geq \log12$?
Jan
7
comment Determining the points of a rotated square.
First line here: en.wikipedia.org/wiki/Rotation_matrix
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 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?