Reputation
Next tag badge:
393/400 score
83/80 answers
Badges
30 343 660
Newest
 Good Answer
Impact
~8.8m people reached

8m
comment How many phone number with $8$ digits exist s.t divide $2,3,5$ and there is no repetitive digit in it?
@NNN: You are welcome.
25m
answered How many phone number with $8$ digits exist s.t divide $2,3,5$ and there is no repetitive digit in it?
54m
comment Show that the Hausdorff topology is unique in a finite set $X$
Let $x_0,x_1, \dots, x_n$ be the points. There is an open set $U_1$ that contains $x_0$ but not $x_1$. There is an open set that $U_2$ that contains $x_0$ but not $x_2$. And so on. The intersection of the $U_i$ is $\{x_0\}$.
2h
comment How to prove that a very large number is not prime
Looks like $10^{21}+1$, divisible by $11$.
4h
answered Every morning the lecturer chooses pairs of students
4h
comment Every morning the lecturer chooses pairs of students
I think it is accessible. Just as a check on your calculations, $\Pr(X=3)=\frac{7}{12}$ (do this one first) and therefore $\Pr(X=1)=\frac{5}{12}$.
5h
comment Every morning the lecturer chooses pairs of students
If $X$ is the number of "mixed" pairs, then indeed the only possibilities are $X=1$ and $X=3$. Are you asked to find the distribution of the random variable $X$?
6h
comment Find a close form expression for $f(x)$
Note that in general $(a_0+a_1x+a_2x^2+\cdots)(1+x+x^2+\cdots)=a_0+(a_0+a_1)x+(a_0+a_1+a_2)x^2+\cdots‌​$
15h
comment Find triples $(a,b,c)$ of positive integers such that…
@almagest: I messed up on the wording. To reword, the smallest of $a,b,c$ is $\le 2$. So examine two cases, (i) smallest is $1$ and (ii) smallest is $2$.
16h
answered Is a divides infinitely many repunits?
17h
comment Incorporating input and output into Diophantine equations
I do not understand the question, but there is no algorithm that will determine, given a Diophantine equation, whether that equation has a solution in the natural numbers (or integers).
17h
comment Calculating the mean and variance of continuous distribution
Your simulation seems to be a simulation of a discrete random variable. All your values are integers.
17h
comment Calculating the mean and variance of continuous distribution
What distribution should we assume? Not clear, but it seems reasonable to assume a continuous distribution.
17h
comment Do monomials form a basis for the vector space of real analytic functions?
Actually, they are I think clearly linearly independent but do not span.
18h
answered If $p>5$ is prime, $2p+1$ is a prime, $\frac{4p+1}{3}$ is prime, $8p+1$ is prime, Then $p \equiv 29 (mod \; 30)$
21h
answered Show that the $C_n \geq 4^{n-1}/2^{n}$ where $C_n$ is the Catalan number
21h
answered Use induction to prove that $2^n \gt n^3$ for every integer $n \ge 10$.
1d
comment How to find sequence of digits in pi?
It is not implausible that every finite sequence occurs, that is the case for "most" real numbers.
1d
comment How to find sequence of digits in pi?
It is not known whether every finite sequence of digits appears in the decimal expansion of $\pi$. The situation is no better for any base.
1d
comment Exhibit isomorphism between $F$ and $F'$
A start: If you decide what $\alpha$ should be mapped to, in terms of $\beta$, or vice-versa, the full mapping will be determined.