Ittay Weiss
Reputation
45,408
373/400 score
 Apr6 reviewed Close How to write ODEFUN's with y prime's? Apr6 reviewed Close Find integer solutions of the following set of equations Apr6 reviewed Close The function $f:G \rightarrow G$ defined by $f(x)=x^2$ is a homomorphism iff G is abelian. Apr6 answered Sequences and real numbers Apr6 comment Do Equal Sets Have the Same Enumerations? CSB to prove $|A|=|B|$.... not a good idea. Apr6 answered Do Equal Sets Have the Same Enumerations? Apr5 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? Apr4 answered If you have a triangle with its mirror reflection, are they congruent? Apr3 comment Why doesn't inequality hold as a property in natural number induction? $n<10$ holds for 9 but fails for 10. Apr2 answered Basis of a basis-linear algebra? Apr2 answered What is mathematical definition of a fluid? Apr2 awarded terminology Apr1 answered What does “hom” stand for in hom-sets and hom-functors? Mar31 comment Rational And Real Numbers Density then yes, if an interval has more than one element, then it has infinitely many. Mar31 comment Rational And Real Numbers Density if you're saying what I think you're saying, what about $\{1,2\}$? Mar31 comment Why doesn't $\pm a = \pm b \implies -a = b$? how would you go about arguing that $a^2=b^2$ implies $-a=b$??? Mar29 awarded Guru Mar28 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. Mar28 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. Mar28 answered Linear Algebra Determinant problem