 # A.K.

 2017 May 26 accepted proving that \$-1\$ and \$1\$ are the only units in \$Z\$, using the given axioms May 26 revised proving that \$-1\$ and \$1\$ are the only units in \$Z\$, using the given axiomsadded 48 characters in body May 26 comment proving that \$-1\$ and \$1\$ are the only units in \$Z\$, using the given axiomsOops, I left out the associativity axioms by mistake! I am intrigued by your comment that the well-ordering axiom might be enough to prove associativity. Are you sure that's true? May 25 comment proving that \$-1\$ and \$1\$ are the only units in \$Z\$, using the given axiomsI did realise that \$0 = 1\$ meant there was only element but - as you said - that couldn't have been the intention. But I'm not sure if the 4th and 5th axioms imply \$0 \neq 1\$. In any case, even after assuming \$0 \neq 1\$. I should've realised - as you pointed out - that the same axioms are satisfied by \$\mathbb{Q}\$ and \$\mathbb{R}\$ so clearly something was missing. Although I like the book's approach (after the one day I spent with it), I'm not sure if missing the additional axiom was intended (maybe it's a feature of the inquiry-based approach?) or an oversight by the authors. May 25 asked proving that \$-1\$ and \$1\$ are the only units in \$Z\$, using the given axioms May 19 comment edge deletions and spanning subgraphsyou're right, I was reading more into the definition of \$G-X\$ than was there! May 19 accepted edge deletions and spanning subgraphs May 19 comment edge deletions and spanning subgraphs@saulspatz that the subgraph induced by removing one or more edges from \$G\$ is necessarily a spanning subgraph of \$G\$, which the text appears to me to be implying. May 18 asked edge deletions and spanning subgraphs May 6 awarded Tumbleweed Apr 29 revised should I be using `UIDocument` and/or `UIDocumentBrowserViewController` in my app?edited tags Apr 29 asked should I be using `UIDocument` and/or `UIDocumentBrowserViewController` in my app? Dec 8 answered Division of Factorials Aug 6 comment strange choice of constant when showing \$an + b = O(n^2)\$ ("Introduction to Algorithms" book)@miracle173 I guess your question stems from lack of context (as I only quoted the text relevant to my question). Taken from the beginning, the sentence actually goes: "What may be more surprising is that when a > 0, any linear function an+b is O(n^2)", the potential "surprise" according to the authors being an+b is not only O(n) but also O(n^2). Aug 6 comment strange choice of constant when showing \$an + b = O(n^2)\$ ("Introduction to Algorithms" book)@miracle173, I know an+b is O(n) (and even \$\Theta(n)\$). That was not the point of the question. Aug 5 awarded Supporter Aug 5 accepted strange choice of constant when showing \$an + b = O(n^2)\$ ("Introduction to Algorithms" book) Aug 5 comment strange choice of constant when showing \$an + b = O(n^2)\$ ("Introduction to Algorithms" book)Why do you feel I should remove it? I think it might help someone else making the same mistake as me. (btw if you were to post your comment as an answer I'd be happy to accept it.) Aug 5 comment strange choice of constant when showing \$an + b = O(n^2)\$ ("Introduction to Algorithms" book)@fade2black ah okay, I had missed the clause that \$0 \le f(n)\$. Thanks! Aug 5 asked strange choice of constant when showing \$an + b = O(n^2)\$ ("Introduction to Algorithms" book)