Question

Suppose that $A$ is an $n \times m$ matrix and $col(A)$ is a subspace of $\mathbb{R}^5$, then what is $n$?

score 72 · Answer 1 · 2026-04-15 14:06:42

72

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Suppose that $A$ is an $n \times m$ matrix and $col(A)$ is a subspace of $\mathbb{R}^5$, then what is $n$?

Published on 15 Apr 2026 - 14:06

score 43 · Answer 2 · 2026-04-14 20:52:41

43

Views

Show that a function is in $H^1(B_1(0))$ with polar coordinates (classical example)

Published on 14 Apr 2026 - 20:52

score 98 · Answer 3 · 2026-04-15 11:08:35

98

Views

Existence of a limit and a counterexample

Published on 15 Apr 2026 - 11:08

score 167 · Answer 4 · 2026-04-16 03:27:36

167

Views

Find a Quotient of Hausdorff spaces not is Hausdorff

Published on 16 Apr 2026 - 3:27

score 179 · Answer 5 · 2026-04-12 05:52:50

179

Views

Is a locally square integrable local martingale locally a square integrable martingale?

Published on 12 Apr 2026 - 5:52

score 258 · Answer 6 · 2026-04-14 05:13:15

258

Views

Example of a space that is Semi-locally Simply connected that is neither Simply connected nor Locally simply connected.

Published on 14 Apr 2026 - 5:13

score 53 · Answer 7 · 2026-04-12 17:55:42

53

Views

What is a property that looks like it holds for all natural numbers but it turns out it doesn't?

Published on 12 Apr 2026 - 17:55

score 98 · Answer 8 · 2026-04-14 19:13:18

98

Views

Find a convex function $f$ which satisfies $\lim\limits_{x\to+\infty}f'(x)=a$ and $\lim\limits_{x\to+\infty}\Big[x\Big(f'(x)-a\Big)\Big]\neq0$

Published on 14 Apr 2026 - 19:13

score 298 · Answer 9 · 2026-04-08 19:49:50

298

Views

What is a counterexample to LaSalle invariance principle?

Published on 08 Apr 2026 - 19:49

score 89 · Answer 10 · 2026-04-14 13:30:51

89

Views

An example of function that is defined everywhere but is not the derivative of any differentiable function.

Published on 14 Apr 2026 - 13:30

score 143 · Answer 11 · 2026-04-12 01:57:31

143

Views

Find where the cut wire theorem fails

Published on 12 Apr 2026 - 1:57

score 17 · Answer 12 · 2026-04-15 10:51:06

17

Views

Existence of partials for all vectors $p$ at origin implies continuity

Published on 15 Apr 2026 - 10:51

score 128 · Answer 13 · 2026-04-08 19:07:38

128

Views

Are continuous bijections between compact and topological spaces homeomorphisms?

Published on 08 Apr 2026 - 19:07

score 313 · Answer 14 · 2026-04-13 06:10:01

313

Views

Does strict convexity everywhere implies strong convexity on a neighborhood of almost every point?

Published on 13 Apr 2026 - 6:10

score 28 · Answer 15 · 2026-04-08 21:58:40

28

Views

Convergence for complex series tests

Published on 08 Apr 2026 - 21:58

List Question

Suppose that $A$ is an $n \times m$ matrix and $col(A)$ is a subspace of $\mathbb{R}^5$, then what is $n$?

Show that a function is in $H^1(B_1(0))$ with polar coordinates (classical example)

Existence of a limit and a counterexample

Find a Quotient of Hausdorff spaces not is Hausdorff

Is a locally square integrable local martingale locally a square integrable martingale?

Example of a space that is Semi-locally Simply connected that is neither Simply connected nor Locally simply connected.

What is a property that looks like it holds for all natural numbers but it turns out it doesn't?

Find a convex function $f$ which satisfies $\lim\limits_{x\to+\infty}f'(x)=a$ and $\lim\limits_{x\to+\infty}\Big[x\Big(f'(x)-a\Big)\Big]\neq0$

What is a counterexample to LaSalle invariance principle?

An example of function that is defined everywhere but is not the derivative of any differentiable function.

Find where the cut wire theorem fails

Existence of partials for all vectors $p$ at origin implies continuity

Are continuous bijections between compact and topological spaces homeomorphisms?

Does strict convexity everywhere implies strong convexity on a neighborhood of almost every point?

Convergence for complex series tests

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