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22:09
@DanielFischer hello, I have a function $F:\Bbb{R}^2\to \Bbb{R}^2$ such that $F(x,y)=(x^2+y^2,y^2)$.
I would like to prove that $\Omega=\{p\in \Bbb{R}^2 ; \lim_{k\to\infty}F^k(p)=0\}$ is a domain, where $F^k$ is the $k$-composed map.
For instance I can, only, prove that $p\in \Omega$ if and only if $F(p)$ is as well in $\Omega$. Don't see how can I prove it's open.
hiya
@MikeMiller what was it you were wanting to tell me about?
cap
cap
22:40
Why isn't $\mathbb{Z}\times \mathbb{Z}$ isomorphic (as rings) to $\mathbb{Z} (\sqrt {2})$?
22:55
cap: What blows up if $(x,y)^2=(2,2)$? (Also, why must $2\in \Bbb Z(\sqrt 2)$ get mapped to $(2,2)$?)
cap
cap
@EricStucky Then 2 has a square root in the integers. Got it.
23:19
is it true that x^2+y^2≥xy?
Subtract 2xy from both sides :)
we get (x-y)^2 ≥ -xy
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