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For posts looking for feedback or verification of a proposed solution. "Is this proof correct?" 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 duplicate questions.

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Prove by induction that $\sum_{i=1}^{k} a^{k-i} b^{i-1}=\frac{a^{k}-b^{k}}{a-b}$

So everything in your proof is correct, but you made a mistake in your first line with indexing. What you actually want to show is $$\sum_{i=1}^{k+1}a^{k+1-i}b^{i-1}=\frac{a^{k+1}-b^{k+1}}{a-b}$$ inst …
mathlearner98's user avatar
4 votes
1 answer
119 views

Konig's tree lemma without using axiom of dependent choice

Konig's tree lemma says that, if $T$ is a rooted tree such that has infinitely many nodes where each node has a finitely many successors, then $T$ has an infinite branch. I think I have a proof (which …
mathlearner98's user avatar
0 votes
1 answer
35 views

Proof Verification: identifying quotient of submodules

Let $M$ be $R$ module, $M_1,M_2,S$ be $R$ submodules of $M$ such that $M_1\subset M_2$. Let $N_1$ be the $R$ submodule of $M$ generated by $M_1$ and $S$, let $N_2$ be the $R$ submodule of $M$ generate …
mathlearner98's user avatar
2 votes
1 answer
76 views

Proving that product of two-point sets is compact

I am reading Jech's Axiom of Choice, and I want to prove: For a non-empty set $I$, if $\{0,1\}^I$, the generalized Cantor space, is non-empty compact, then $\prod_{i\in I}A_i$ where $|A_i|=2$ for all …
mathlearner98's user avatar
4 votes
0 answers
110 views

Prime Ideal Theorem implies Hahn Banach Theorem

I am reading Jech's Axiom of Choice, and there is this exercise: chapter 2 Problem 19: Show that the Hahn-Banach Theorem follows from the Prime Ideal Theorem. I came up with a (possibly wrong) proof …
mathlearner98's user avatar