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Apr
6
reviewed Close How to write ODEFUN's with y prime's?
Apr
6
reviewed Close Find integer solutions of the following set of equations
Apr
6
reviewed Close The function $f:G \rightarrow G$ defined by $f(x)=x^2$ is a homomorphism iff G is abelian.
Apr
6
answered Sequences and real numbers
Apr
6
comment Do Equal Sets Have the Same Enumerations?
CSB to prove $|A|=|B|$.... not a good idea.
Apr
6
answered Do Equal Sets Have the Same Enumerations?
Apr
5
comment Prove the following is a homomorphism and describe its kernel.
this can't possibly be correct. How do you go from $x+y$ to $f(x)+f(y)$? what is $f(x)$ or $f(y)$ for that matter???? (answer: nothing, as it is undefined). Look closely at the domain for $f$. What is the group operation on the domain?
Apr
4
answered If you have a triangle with its mirror reflection, are they congruent?
Apr
3
comment Why doesn't inequality hold as a property in natural number induction?
$n<10$ holds for 9 but fails for 10.
Apr
2
answered Basis of a basis-linear algebra?
Apr
2
answered What is mathematical definition of a fluid?
Apr
2
awarded  terminology
Apr
1
answered What does “hom” stand for in hom-sets and hom-functors?
Mar
31
comment Rational And Real Numbers Density
then yes, if an interval has more than one element, then it has infinitely many.
Mar
31
comment Rational And Real Numbers Density
if you're saying what I think you're saying, what about $\{1,2\}$?
Mar
31
comment Why doesn't $\pm a = \pm b \implies -a = b$?
how would you go about arguing that $a^2=b^2$ implies $-a=b$???
Mar
29
awarded  Guru
Mar
28
comment Why do we believe that $\sum_{k=1}^{\infty} x_k=\sum_{i=1}^{\infty}\sum_{j=1}^{\infty}x_{ij}$?
the equality is not obvious. The notation is indeed just a limit (but a limit is just a number), and establishing the equality requires proof. Your question suggests that you may not completely understand the notion of a limit, or that you don't quite understand the proof of the theorem in question.
Mar
28
comment Why do we believe that $\sum_{k=1}^{\infty} x_k=\sum_{i=1}^{\infty}\sum_{j=1}^{\infty}x_{ij}$?
perhaps you are lacking knowledge of the theorem that states that an absolutely convergent series can be rearranged in any way, and parenthesis can be inserted in any way (including wrapping infinitely many elements), and the resulting series will have the same sum.
Mar
28
answered Linear Algebra Determinant problem