Reputation
31,259
Next tag badge:
97/100 score
30/20 answers
Badges
2 30 63
Newest
 Nice Answer
Impact
~175k people reached

2d
answered What is the value as this sequence tends to infinity?
2d
comment what is the expected value of $x^TAx$?
Without determining the distribution of $x$, this is impossible.
2d
comment Determining sets using basic operations
On this site, it is usual that you accept and upvote the answer that was helpful to you. That way, the matter can be considered closed.
Jul
28
awarded  Nice Answer
Jul
28
answered Must all Lebesgue integrable functions really be invertible?
Jul
27
comment Is the real number $\sqrt{6}$ in $\mathbb{R}$ equal to the 5-adic number $\sqrt{6}$ in $\mathbb{Q}_5$?
@oxeimon Yeah, all the tens should have negative powers...
Jul
27
comment Is the real number $\sqrt{6}$ in $\mathbb{R}$ equal to the 5-adic number $\sqrt{6}$ in $\mathbb{Q}_5$?
@C.Christopher I made a mistake. My comment was wrong. In fact, the answer is yes. You can find such numbers $a_0, a_1,\dots$ that $\sum_{i=0}^\infty a_ip^i = \sqrt 6$. Simply take $b_n$ which is the $n$-th number in the decimal expansion of $\sqrt 6$ and set $a_n = \frac{b_n10^n}{p^n}$. That way, the original sum becomes $$\sum_{i=0}^\infty b_i 10^i$$ which is $\sqrt 6$.
Jul
27
comment Is the real number $\sqrt{6}$ in $\mathbb{R}$ equal to the 5-adic number $\sqrt{6}$ in $\mathbb{Q}_5$?
What do you mean by "equal" in this case?
Jul
27
comment Determining sets using basic operations
@Jennifer My pleasure. On this site, it is usual that you accept and upvote the answer that was helpful to you. That way, the matter can be considered closed.
Jul
27
comment Determining sets using basic operations
@Jennifer No. There is one element in $A$ which is also in $\{\emptyset\}$.
Jul
27
comment Determining sets using basic operations
@Jennifer Precisely! Now, what about the answer to $e$?
Jul
27
comment Determining sets using basic operations
@Jennifer No. Try to slowly read through my comment. Then, for every element of $A$, ask yourself: "is this an element of $A\setminus \emptyset$?" Then tell me for which elements you answered "no", and why.
Jul
27
revised Determining sets using basic operations
added 231 characters in body
Jul
27
answered Determining sets using basic operations
Jul
27
comment Determining sets using basic operations
That's like saying that $x=2$ and then saying $x_3$ is the number $x$ which is greater than $3$. It makes no sense.
Jul
27
comment Determining sets using basic operations
But $A$ does not contain $a,b$ and $c$. You already defined what $A$ is.
Jul
27
comment Determining sets using basic operations
What does $A\{a,b,c\}$ even mean?
Jul
27
comment Normalizing a basis
@jmiller using the scalar product you described, and knowing that $1=1+0\cdot x + 0\cdot x^2$, it is obvious that $\langle1,1\rangle = 4\cdot 1\cdot 1 + 2\cdot 0\cdot 0 + 0\cdot 0 = 4$.
Jul
27
comment Find expression in terms of x
@Emma Also, mathematics is a skyscraper, and if your fifth floor keeps collapsing, it may be because you haven't built a first floor yet. In this metaphor, linear algebra and solving linear eqations is the first floor, and integration is the fifth.
Jul
27
comment Find expression in terms of x
@Emma Two equations for two variables. What do we usually do in such a case?