# Matt Pressland

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bio website people.bath.ac.uk/mdp33 location Bath, United Kingdom age 25 member for 2 years, 10 months seen 2 days ago profile views 924

Postgraduate student at the University of Bath, UK, studying geometry and representation theory. Currently thinking about cluster algebras and related objects.

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 Nov10 comment Smallest Subring of R that contains $S \cup \{a\}$ You seem to be thinking along the right lines. Can you show that any subring $S'$ containing $S\cup\{a\}$ in fact contains the set in question? This is enough to show that your set is contained in the intersection of all subrings containing $S\cup\{a\}$, and the other direction is easy since you have already shown that your set is such a subring. Nov10 comment Prove that $(x^3-2)$ is a maximal ideal of $\Bbb Q[x]$ To get better answers, you should add some context to your question - what have you already tried? Do you know some theorems that might help? For example, would it help you to know that $x^3-2$ is irreducible? Can you prove that it is? Nov7 comment Proving that $f$ is a bijection. @egreg I'm not sure I'm following - the OP has a definition ($g(y)=x\iff f(x)=y$) in the question. Nov6 comment Proving that $f$ is a bijection. It doesn't appear to be the definition the OP is using, given the phrasing of both the problem they are trying to solve and the clause beginning "I basically need to show...". Nov6 answered Proving that $f$ is a bijection. Nov6 answered Semisimple submodule Nov6 reviewed Approve I love maths, but my school is limited in its teachings. Nov5 comment Give a counterexample to show that $(AB)^{-1} \neq A^{-1}B^{-1}$ To make the same point in another way - it is not true that $AB\ne BA$ for all $A,B$, but there do exist some $A,B$ for which $AB\ne BA$ - so find a pair (that are also invertible), and you have an explicit counterexample. Nov5 comment Shape of the visible part of the Moon Pas de problème. ;) I have just discovered that both of these things are "ellipse" in French, which makes your mistake even more forgivable than it already was! Nov5 comment Shape of the visible part of the Moon Since you asked for language corrections - I'm pretty certain that you meant "ellipse" in "other cases". This is the shape (singular of ellipses), whereas ellipsis refers to the three dots immediately preceding the word! Nov5 revised Shape of the visible part of the Moon deleted 1 character in body Nov5 comment re-writing a mathematical expression @EmmaTebbs I agree this is a slightly difficult question to tag - myself and another user have now retagged it. Physics and matlab are both relevant to the context, and I also added algebra-precalc because it's essentially about manipulating expressions (although the expressions are a little more involved than those that would normally occur under this tag!). Nov5 revised re-writing a mathematical expression edited tags Nov5 comment re-writing a mathematical expression @EmmaTebbs They also use $f$ again in a second expression on the next page, so its more efficient to define it separately. (It also prevents the formula from $K_{\mathrm{int}}$ from breaking over three lines, which would make it harder to read.) Nov4 awarded Nice Answer Nov4 comment Can basis vectors have fractions? @Bill Since my point was that the operation of clearing denominators doesn't make sense in general, it didn't seem worth identifying the most general situation in which it does makes sense. Nov4 revised $f(x)=x^p-a$ is either ireducible or has a root? added 36 characters in body Nov4 comment $f(x)=x^p-a$ is either ireducible or has a root? Your first assertion is false; if $k=\mathbb{R}$ or $k=\mathbb{C}$, then $f$ is not irreducible for most values of $p$, by the fundamental theorem of algebra. Nov4 revised Can basis vectors have fractions? added 134 characters in body Nov4 answered Can basis vectors have fractions?