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age 25
visits member for 3 years, 11 months
seen Sep 1 at 3:13

A dropout struggling to finish Harris's AG book.


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revised How can I prove that $xy\leq x^2+y^2$?
added 637 characters in body
Aug
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comment How can I prove that $xy\leq x^2+y^2$?
@ronno Not really, because $X := \mathbb{R}^2 \setminus \{x = -y\}$ is dense in $\mathbb{R}^2$, and $[0, +\infty)$ is closed in $\mathbb{R}$, therefore its pullback along $(x, y) \mapsto x^2 - xy + y^2$ must be $\operatorname{cl}X = \mathbb{R}^2$. Of course it is too technical for a precalculus-level question.
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awarded  Good Question
Mar
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revised How can I prove that $xy\leq x^2+y^2$?
Removed dickishness
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awarded  Popular Question
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awarded  Notable Question
Aug
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comment Rigour in mathematics
@RobertIsrael Suppose there is a proposition, and you can prove that it is impossible to construct a counterexample to it. Is this proposition true?
Aug
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awarded  Nice Answer
Aug
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answered Rigour in mathematics
Jul
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comment How do I find partners for study?
I think Reddit University kind of fits your description.
May
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revised Properties of Continuous Functions
[Edit removed during grace period]
May
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answered Properties of Continuous Functions
May
21
comment Can an algebraic structure have indistinguishable elements?
More like indistinguishable points of $\operatorname{Spec}\mathbb{R}[x]$ - kinda.
May
13
comment Rotate a plane along a line in 3d space
@cortical BTW, your link is about affine geometry, which also deals with translations, and it uses projective geometry to represent affine transformations with matrices. Beautiful stuff!