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3h
comment What is the probability that a psychic correctly “predicts” the outcome of at least 5 out of 10 coin flips?
yes${}{}{}{}{}$
19h
answered What is the probability that a psychic correctly “predicts” the outcome of at least 5 out of 10 coin flips?
19h
revised Smallest $n$ such that $U(n)$ contains a subgroup isomorphic to $\mathbb Z_5 \oplus \mathbb Z_5$
added 707 characters in body
19h
answered Smallest $n$ such that $U(n)$ contains a subgroup isomorphic to $\mathbb Z_5 \oplus \mathbb Z_5$
20h
comment How I can prove that for any natural number $n$ such that $30<n$, $\pi(4n-3)<n$?
it is true, we have $\pi(x)<1.3\frac{x}{\log x}$ for $x\leq 17$
20h
answered Is $S_1\cap S_2$ and $S_1\setminus S_2$ always linearly dependent if $S_1$ and $S_2$ are linearly dependent subsets of vector space $V$?
23h
comment Show that $1^k+2^k+\cdots+n^k$ is $\Omega (n^{k+1})$
because $1^k+2^k+3^k+\dots+n^k=\int\limits_0^n\lceil x \rceil ^kdx\leq\int\limits_0^n x ^kdx$
2d
revised Show that $1^k+2^k+\cdots+n^k$ is $\Omega (n^{k+1})$
added 150 characters in body
2d
revised Show that $1^k+2^k+\cdots+n^k$ is $\Omega (n^{k+1})$
added 150 characters in body
2d
revised Show that $1^k+2^k+\cdots+n^k$ is $\Omega (n^{k+1})$
added 4 characters in body
2d
answered Show that $1^k+2^k+\cdots+n^k$ is $\Omega (n^{k+1})$
2d
answered Show that an inverse of a bijective linear map is a linear map.
2d
comment Is there an arbitrarily large set of naturals so that the sum of each two has exactly $n$ prime divisors? What about an infinite set?
exactly $n$ prime divisors right?
2d
awarded  Nice Answer
Feb
6
answered Expected value problem with cars on a highway
Feb
6
comment Expected value problem with cars on a highway
what do you mean each prefered speed is taken at random? for every car we pick a speed in $\mathbb R^+$ using a some distribution?
Feb
5
comment Prove that a one-color $K_4$ exists in a two-color $K_{18}$
yes, suppose there are $18$ vertices, pick a vertex $v$, then at least $9$ blue edges come out of $v$ or at least $9$ red edges come out of $v$. in the first case notice there is a blue $K_3$ inside the $K_9$ or a red $K_4$, if there is a blue $K_3$ it turns into a blue $K_4$ after adding the vertex $v$. The case in which there are $9$ red edges is analogous.
Feb
5
comment Prove that a one-color $K_4$ exists in a two-color $K_{18}$
you can find $K_{17}$ colored red and blue with blue or red $K_4$ here
Feb
5
comment Prove that a one-color $K_4$ exists in a two-color $K_{18}$
Happy to help, tell me if something is unclear.
Feb
5
revised Prove that a one-color $K_4$ exists in a two-color $K_{18}$
edited body