39,294 reputation
13774
bio website zakuski.utsa.edu/~jagy
location Berkeley, CA
age 57
visits member for 3 years, 3 months
seen 3 hours ago

I put an email address here and intended it to be visible. In case it is not, search with my last name at http://www.ams.org/cml/

See me at http://mathoverflow.net/users/3324/will-jagy

and http://zakuski.utsa.edu/~jagy/ and

http://zakuski.math.utsa.edu/~kap/forms.html and

http://arxiv.org/find/math/1/au:+Jagy_W/0/1/0/all/0/1

If people would include the source of a given problem as part of the process of posting a question, life would be a little easier.


6h
comment Does x + y have a maximum value under the following conditions?
get some graph paper and draw a really, really careful picture of the feasible region, meaning the region where all four given inequalities apply.
6h
comment Looking for a alternative forms of p = x(x+p)^y
what does the phrase "algebraic data type" mean?
9h
comment Which integers are representable by $x^2+2y^2+7z^2$?
Even the raw list of regular forms goes over the 30,000 character limit for answers here.
9h
comment Which integers are representable by $x^2+2y^2+7z^2$?
I have everything; all but one are small enough to email. These are text files, just as the output I put below. Anyway, use my gmail address.
10h
comment Which integers are representable by $x^2+2y^2+7z^2$?
complete genera are available at math.rwth-aachen.de/~Gabriele.Nebe/LATTICES/Brandt_1.html with any mixed term coefficients even. Choices in reduction may vary slightly from my current tables.
10h
comment Which integers are representable by $x^2+2y^2+7z^2$?
@Tahs posted second answer
10h
answered Which integers are representable by $x^2+2y^2+7z^2$?
11h
revised Which integers are representable by $x^2+2y^2+7z^2$?
added 1576 characters in body
11h
revised Which integers are representable by $x^2+2y^2+7z^2$?
added 1576 characters in body
11h
answered Which integers are representable by $x^2+2y^2+7z^2$?
11h
answered Understanding Dynkin Diagrams - any organising ideas - are they now adequately understood?
12h
revised Prime as sum of three numbers whose product is a cube
added 930 characters in body
14h
comment Show that $ax^2+2hxy+by^2$ is positive definite when $h^2<ab$
First multiply by $4a$
15h
comment Show that $ax^2+2hxy+by^2$ is positive definite when $h^2<ab$
actually, $h^2 < ab $ says definite (complete the square), then $a > 0$ says positive definite and $a < 0$ says negative definite.
1d
comment Calculating volume of spherical wedge from parallelepiped corner
Angles between each face?
1d
answered Prime as sum of three numbers whose product is a cube
1d
comment Prime as sum of three numbers whose product is a cube
if $p = x^2 + x y + y^2$ with $x>0$ but $y<0,$ and $x+y > 0,$ we also have $p = (x+y)^2 + (x+y)(-y) + (-y)^2$ with both positive. If $x+y < 0,$ then $p = x^2 + x(-x-y) + (-x-y)^2$
1d
comment Proof $p(A)=0$ without Cayley-Hamilton theorem when $A$ is upper triangular
Write it out in detail, all symbols, for $n=2$ and $n=3.$ With small $n$ you can see exactly how $p(x)$ factors and how to interpret $(x-c_j)^{r_j}$ when $x=A$
1d
comment Minimum surface attaching two parallel (non-planar) circles.
en.wikipedia.org/wiki/Catenoid
2d
comment How to find the domain and range of $f(x) = \sqrt{x^2-2x+5}$?
NOT graphing calculator. Human being and graph paper, which has little squares on it.