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Sep
10
comment Is there a power of 2 that, written backward, is a power of 5?
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Sep
9
comment If $P \leq G$, $Q\leq G$, are $P\cap Q$ and $P\cup Q$ subgroups of $G$?
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Sep
9
comment Tricks to Prove Union of Two Subgroups iff One is Contained in the Other - Fraleigh p. 54 - based on Exercise 5.4.5
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Sep
9
comment Let H, K be subgroups of a group G. If H U K is a subgroup of G, then H is subset of K and K is subset of subset H
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Aug
25
comment Proof that the set of all functions from $\mathbb N$ to $\mathbb N$ is not enumerable
@Guilherme D Look at this
Aug
24
comment How can I show why this equation has no complex roots?
Yes, sorry I didn't see them. The problem is that I'm not sure you can cancel out .
Aug
24
comment How can I show why this equation has no complex roots?
$$1,2,\ldots,n$$
Aug
24
comment How can I show why this equation has no complex roots?
There are more roots of $F_{n+2} = F_n$other that those of your last equation. Any root of $F_n = 0$ would be a root of $F_{n+2} = F_n$.
Aug
16
comment Show that $\mathbb Z[x]$ and $\mathbb Q_{>0}$ are isomorphic
This question has been already asked
Aug
6
comment How to prove that $\det\left[\pmatrix{u_1 & v_1\\ u_2 & v_2\\ u_3 & v_3}\pmatrix{s_1 & s_2 & s_3\\ t_1 & t_2 & t_3}\right]=0$?
@Nishant you're right, let me correct myself: Let $A$ be a $m\times n$ matrix and $B$ be a $n\times m$ matrix. If $n\lt m$ then $AB$ is not invertible.
Aug
3
comment Proof for '$AB = I$ then $BA = I$' without Motivation?
I've found this which solves it for $n=2$.
Jul
6
comment Polynomial Linear transformation
As in 11.1, let $V$ be $n$-dimensional over... you are confusing that $V$ with the vector space of polynomials. That $V$ is any space, not necessarily that one.
Jul
2
comment If $f^{n_o}$ has a fixed point , then does $f$ also has a fixed point , where $f$ is continuous on $\mathbb R$?
True, but this function is not from $\mathbb R$ into $\mathbb R$ so this doesn't answer the question.
Jun
25
comment Countable union of cartesian product.
It's never an interval. What you en up with looks like stairways.
Jun
23
comment proof by induction that every non-zero natural number has a predecessor
A bit technical answer.
Jun
23
comment Proof for Integral Inequality $|\int f| \le \int |f|$ - is it sufficient enough?
@user2637293 I edited my answer. If anything is unclear, let me know how I can help you.
Jun
21
comment showing $\int _a^b\left(f'\left(x\right)\right)dx\:=\:f\left(b\right)-f\left(a\right)$
@TonyPiccolo That's what he's asking
Jun
12
comment Show: $M\subset\mathbb{R}^n$ Jordan-measurable, iff $vol^*(\partial A)=0$
Look at this
Jun
11
comment $\sqrt a$ is either an integer or an irrational number.
From your handout, when $n$ is not a perfect $k$th power, $\sqrt[k]{n}\not\in\Bbb Q$. What happen with $\sqrt[k]{r}$ for rational and positive $r$?
May
2
comment Showing that $\|f\|_p\to\|f\|_{\infty}$
Many times indeed. Click in here and then look at the Linked column