Questions tagged [solution-verification]
For posts looking for feedback or verification of a proposed solution. "Is this proof correct?" or "where is the mistake?" is too broad or missing context. Instead, the question must identify precisely which step in the proof is in doubt, and why so. This should not be the only tag for a question, and should not be used to circumvent site policies regarding duplication.
46,230 questions
-1 votes
0 answers
18 views
CW-structure on $ X = S^1\times\partial D^2 \;\cup\; \{x,y\}\times D^2 \subset T=S^1\times D^2. $
Considering the space, $ X = S^{1} \times \partial D^{2} \,\cup\, \{x, y\} \times D^{2}. $ the subspace of the solid torus $ S^{1} \times D^{2} $ given by the union of the boundary of the boundary ...
0 votes
0 answers
45 views
Number of solutions to $x^2 - y^2 = n $ in $\mathbb{Z}_m$
Let $n \in \mathbb{Z}_{2^q}$ such that $ n \equiv 2^r m \pmod{2^q}$ for some odd $m$ and $1\leq r<q$. Then the number of solutions to the congruence $x^2 - y^2 \equiv n \pmod{2^q}$ is $(r-1)2^q$. ...
0 votes
2 answers
34 views
About the relationship between flatness as R-module of an ideal K of a commutative ring R and the flatness of the quotient R/K
I sketch a proof of the following assert: If R is a commutative ring with unit an I is an ideal of R, such that R/I is a flat R-module, then I is a flat R-module. It sounds too nice to be true, and I ...
2 votes
2 answers
106 views
Continuity and Differentiability of $|x|^x$
I am working on the following problem from the L’Hôpital’s Rule section of Stewart Calculus, and I would appreciate feedback on whether my approach is sound, as well as clarification on a few things. ...
3 votes
1 answer
91 views
Proof verification: If $A$ and $B$ are independent, then $A'$ and $B'$ are independent
I am trying to prove that if two events $A$ and $B$ are independent, their complements $A'$ and $B'$ are also independent. Given: $$P(A \cap B) = P(A)P(B)$$ Target: $$P(A' \cap B') = P(A')P(B')$$ Here ...
2 votes
1 answer
122 views
Preimage of a connected space in its covering space
Exercise 53.3 of Munkres's Topology asks: Let $p:E\rightarrow B$ be a covering map; let $B$ be connected. Show that if $p^{-1}(b_0)$ for some $b_0\in B$ has $k$ elements, then $p^{-1}(b)$ has $k$ ...
0 votes
1 answer
125 views
How do I find the domain of the function $f(x)=\sqrt{\log(\log x)-\log(4-\log 3)-\log 3}$?
Tricky question to find the domain $$f(x)=\sqrt{\log(\log x)-\log(4-\log 3)-\log 3}$$ My attempt $\log(\log x)-\log(\frac{4}{\log 3})-\log 3=\log(\log x)-(\log(\frac{4}{\log 3})+\log 3) $ $=\log(\log ...
0 votes
0 answers
95 views
Is my proof wrong? The length of AE seems to be 64/11 but i got 6 [closed]
[A triangle ABC circumscribes a circle with center O and radius 4,the point of contact between the incircle and AB is at F and at AC it is E and at BC it is D,the lengths of BD is 6,CD=10, find AE] $$(...
5 votes
1 answer
153 views
Can $p(\lambda)=\lambda^3 -2\lambda^2+\lambda$ be the characteristic polynomial of a linear difference equation?
Question: Let $$p(\lambda) =\lambda^3 -2\lambda^2+\lambda. $$ Can $p(\lambda)$ be the characteristic polynomial of a linear difference equation? Justify. My answer: Yes, because there exists a ...
8 votes
0 answers
90 views
Smooth immersion is a local embedding
I read Theorem 4.25 in Lee's Smooth Manifolds book. This theorem states that a smooth map $F:M\rightarrow N$ is a smooth immersion if and only if it is locally a smooth embedding (let's ignore in this ...
2 votes
0 answers
101 views
$(X, \Sigma, \mu)$ finite measure space and $(f_n)_{n\in\mathbb{N}}$ is sequence in $L^p(X)$. If $f_n \to f$ uniformly on $X$, then $f \in L^p(X)$.
Help in understanding a proof written by a teacher on the following theorem. Let $(X, \Sigma, \mu)$ be a finite measure space and let $(f_n)_{n\in\mathbb{N}}$ be a sequence of functions in $L^p(X)$. ...
6 votes
0 answers
72 views
Is the PB–Basic–007 “solution” in DeepSeek-Math-V2 correct? Possible flaw in its convex-hull argument
I was reading the solution provided for PB–Basic–007 in the DeepSeek-Math-V2 IMO-ProofBench-Basic dataset, and I am unsure whether one of its main steps is valid. I would like to confirm whether I am ...
3 votes
0 answers
118 views
Intersections of Families of Closed Sets under $MA_{\omega_1}$ and under CH
I am studying the following problem: Consider a family $K_\alpha$ ($\alpha<\omega_1$) of closed subsets of $[0,1]$ such that $\mu(K_\alpha)>0.22$, where $\mu$ denotes Lebesgue measure. (a) ...
0 votes
1 answer
184 views
Let$\ \ f:[0,1]\to \mathbb{R}$ be a continuous function. Prove $\ \ \lim_{\lambda\to\infty}\int_0^1 f(x)\sin(\lambda x)\,dx = 0$. [duplicate]
NOTE- The source of question is Advanced Calculus on real axis which doesn't cover $\textsf{Lebesgue integral}$ and $\textsf{Measure Theory}$ so therefore an approach by those wouldn't be of much ...
1 vote
2 answers
119 views
Showing that $\nexists r \in \mathbb{Q} : 2^r=3$
I am currently self studying real analysis from the book Understanding Analysis, Stephen Abbott, 2nd edition. In page 11, exercise 1.2.2 the problem asks to show that there is no rational $r$ ...