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Jun
30
comment Logic problem involving sum of digits
@Mike: you are right, but I mentioned that one can construct other solutions by adding/removing zeros
Jun
30
comment Complex numbers $z$ satisfying $|z−a|+|z+a| = 2|b|\Leftrightarrow |a|\le |b|$.
If you draw the complex numbers as points in the plane your equation describes what kind of figure?
Jun
30
comment Complex numbers $z$ satisfying $|z−a|+|z+a| = 2|b|\Leftrightarrow |a|\le |b|$.
What is the first implication and what is the second one? Please show us the prove.
Jun
30
comment Are 7 and 49 coprime?
@Ben: better than "Thanks": accept the answer.
Jun
30
comment Logic problem involving sum of digits
$11101110111^2=123234645696546432321$ is another one
Jun
30
comment Logic problem involving sum of digits
@Donkey Kong: No, $S(n^2)$ means squaring the number $n$ and then taking the sum of digit.
Jan
16
comment Cubes differences and primality
I completed the prove, I hope there are no errors. But I can't see how that will help you to avoid trial an error. Can you explain this?
Jan
16
comment Cubes differences and primality
@Ross Millikan, thank's
Jan
12
comment Is there an intuitive explanation for $ x^2+y^2=7 z^2 $ doesn't have any integer solution?
I still I can't see where you use the fact that $x^2+y^2=z^2$ has infinite integer solutions.
Jan
12
comment Is there an intuitive explanation for $ x^2+y^2=7 z^2 $ doesn't have any integer solution?
That is neither a answer to the question ("Does this fact ...") nor does this give us a complete answer to the more usefull question: what are the integer solutions of the equation.
Jan
10
comment how can I prove that $\frac{\arctan x}{x }< 1$?
@enzolib: thanks, I added this to the answer.
Jan
9
comment How do I find which set of functions is linearly independent?
and how do you prove that all other are not linear dependent?
Jan
5
comment Better way of factorising $x^2-a^2+x+a$
here is a more systematic technic math.stackexchange.com/a/544042/11206 but maybe much more than you want.
Jan
5
comment Better way of factorising $x^2-a^2+x+a$
+1, but maybe incomprehensibly to the OP
Jan
5
comment Better way of factorising $x^2-a^2+x+a$
$x({1^2}+1)-a(1^2-1)$ equals $2x$ and not ${x^2}-{a^2}+x+a$. As Hurkyl already noted, your attempt to create a common factor contains an error.
Jan
5
comment Find least possible number of factors
Where can I see that this is a multiple choice question?
Jan
5
comment Find least possible number of factors
Due to what constraint?
Jan
5
comment Find least possible number of factors
you are missing a lot of other cases you have to check
Jan
5
comment Find least possible number of factors
It would be nice if you can change it to a readable format using latex. I did the first few lines for you as an exapmle.
Jan
5
comment Find least possible number of factors
you cannot assume that $AB has exactly three prime factors. It is possible that it has only two or one prime factor.