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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?
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
Apr
18
awarded  Popular Question
Apr
6
comment Proving $\sqrt 3$ is irrational.
Getting a downvote two years later - priceless!