wj32

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bio	website	wj32.org
	location	Australia
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visits	member for	10 months
	seen	3 hours ago
stats	profile views	311

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74 Answers

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12	Is there a short proof of $x^2=(-x)^2$ in an arbitrary ring?
8	Evaluate: $\sum_{n=2}^\infty \frac{n(n-1)}{2^{n-2}}$
7	Number of solutions of $ x_1 + x_2 + … + x_g \le n$
6	How to show $T$ is not one-one and $T$ is not ont0?
6	Is there any function where $f \circ f = f$ but $f(0) = 1$

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2,234 Reputation

+30	Proof of: If $x_0\in \mathbb R^n$ is a point of local minimum of $f$, then $\nabla f(x_0) = 0$.
+45	Prove that the only operator on $\mathbb{C}$ for which his inner product is zero is zero
+20	What exactly are the “higher order terms” (H.O.T.) in Taylor series expansion in multivariable case?
+10	Coordinate-free proof of $\operatorname{Tr}(AB)=\operatorname{Tr}(BA)$?

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8 Questions

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16	Why do my algebra proofs seem like “magic”? Is this related to category theory?
8	Universal property of free module, “converse”
5	Determinant of the transpose via exterior products
4	$x\mapsto f(x^{1/p})$ is smooth if and only if $f^{(n)}(0)=0$ whenever $p\nmid n$
4	Connected manifold + hole = connected manifold?

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58 Tags

42 linear-algebra × 24	14 ring-theory × 2
25 homework × 10	13 real-analysis × 13
18 combinatorics × 8	10 calculus × 7
18 matrices × 6	10 discrete-mathematics × 3
14 abstract-algebra × 6	9 functions × 4

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	Stack Overflow	3,980 rep	1923
$Mathematics Stack Exchange$	Mathematics	2,234 rep	1118

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