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minh quý lê's user avatar

11 votes

4 answers

350 views

Evaluate: 4ドル^9-\binom{8}{1}4^8+\binom{7}{2}4^7-\binom{6}{3}4^6+\binom{5}{4}4^5$

minh quý lê

true blue anil's user avatar

7 votes

2 answers

1k views

Why does this method work some of the time (but only some?)

true blue anil

49.6k

modified 17 hours ago

11 votes

1 answer

802 views

Why do these valleys in $LCM(P_n - 1, P_n + 1) \bmod n$ exist and are they random?

philipxy's user avatar

philipxy

modified Nov 18 at 11:45

6 votes

2 answers

464 views

Cutting a Möbius strip in thirds. Why are the resulting strips interlinked?

heropup's user avatar

heropup

146k

Bruno Andrades's user avatar

9 votes

1 answer

486 views

Do division rings have algebraic closures?

KCd's user avatar

KCd

modified Nov 19 at 15:01

3 votes

2 answers

389 views

Coloring a graph with K-colors

Bruno Andrades

5,334

modified Nov 19 at 12:01

6 votes

4 answers

346 views

Expectation of an absolute value

Greg Martin's user avatar

Greg Martin

94.2k

7 votes

3 answers

298 views

Telescopic series: how to identify it after breaking it down into partial fractions?

xpaul's user avatar

xpaul

49.4k

Noah Schweber's user avatar

4 votes

1 answer

268 views

Examples of countable non-commutative division rings

abstract-algebra

Noah Schweber

264k

modified Nov 20 at 16:56

6 votes

2 answers

197 views

When does $a^n+1$ have $n$ divisors?

Dietrich Burde's user avatar

Dietrich Burde

143k

modified Nov 19 at 18:36

5 votes

2 answers

137 views

Construction of a dense linear order with 2ドル^\kappa$ cuts

Holo's user avatar

Holo

10.6k

modified 16 hours ago

5 votes

2 answers

276 views

Induced Topological Vector Space Structure?

Man-I-Fold's user avatar

Man-I-Fold

Paramanand Singh's user avatar

4 votes

5 answers

209 views

Why is the expansion of numbers in other bases always in base 10ドル$?

number-systems

Dan's user avatar

Dan

19.2k

answered Nov 19 at 17:34

8 votes

2 answers

267 views

Show that if $\frac{f'}{g'}$ increases, then $\frac{f}{g}$ is increasing

Paramanand Singh ♦

92.9k

answered Nov 17 at 20:48

3 votes

2 answers

404 views

The intuition behind defining trigonometric functions in the complex plane as special combinations of exponential functions [closed]

user494137's user avatar

user494137

answered Nov 17 at 19:04

2 votes

2 answers

256 views

How does one derive involutivity of complement from the axioms of a Boolean algebra?

Alex Kruckman's user avatar

Alex Kruckman

88.8k

answered yesterday

3 votes

3 answers

328 views

How many ways to arrange BOOKKEEPER where two E’s appear consecutively but not three.

true blue anil's user avatar

true blue anil

49.6k

answered Nov 20 at 6:30

3 votes

2 answers

151 views

In the Pell's equation $a^2-2b^2=1,ドル is $a$ always of the form $k^2\pm 1$?

J. W. Tanner's user avatar

J. W. Tanner

64.5k

1 vote

6 answers

167 views

Calculating $i^{3/2}$ in two ways gives different results [closed]

complex-numbers

Dan's user avatar

Dan

19.2k

Noah Schweber's user avatar

3 votes

2 answers

272 views

Recursively enumerable sets and the natural numbers

computability

Noah Schweber

264k

answered Nov 19 at 0:51

6 votes

1 answer

266 views

Where to find Nardin's lecture notes on stable homotopy theory?

Scientifica's user avatar

Scientifica

9,088

answered Nov 17 at 15:27

6 votes

1 answer

244 views

Quotient group technicality

Derek Holt's user avatar

Derek Holt

98.3k

Daniele Tampieri's user avatar

3 votes

3 answers

238 views

Analytic sum of an alternating series$\sum\limits_{n=1}^{\infty}(-1)^{n} \frac{n}{\left(n+\sqrt{a+n^2}\right)^2}$

Svyatoslav's user avatar

Svyatoslav

21.5k

modified 11 hours ago

2 votes

4 answers

238 views

Finding the angles of a non-equilateral $\triangle ABC$ with centroid $G$ such that $\angle GAB=\angle GCA=30^\circ$

mezzoctane's user avatar

mezzoctane

1,503

modified 21 hours ago

2 votes

2 answers

168 views

How can the integral $\int_{0}^{\infty} \left(\frac{\sin x}{x}\right)^3dx$ be calculated? [duplicate]

Renato C's user avatar

Renato C

modified 9 hours ago

2 votes

2 answers

250 views

Does the Axiom Schema of Separation in any sense "provide" only countably many definitions of subsets of $\mathbb{N}$?

NikS's user avatar

NikS

2,303

modified 20 hours ago

4 votes

1 answer

275 views

Can an absolutely convergent infinite linear combination of an algebraically independent family be algebraic?

KELVIN LAM's user avatar

KELVIN LAM

modified Nov 19 at 2:40

3 votes

1 answer

164 views

Can 1,ドル \sqrt{26},5$ construct a right angle triangle?

Math12's user avatar

Math12

modified 9 hours ago

0 votes

1 answer

117 views

Is the matrix A invertible? [closed]

linear-algebra

Daniele Tampieri

modified Nov 17 at 5:30

4 votes

1 answer

143 views

if $x^2+1$ is a powerful number then $x=682$?

Bill Dubuque's user avatar

Bill Dubuque

285k

modified 4 hours ago

3 votes

2 answers

222 views

Showing the Cayley transform sends positive definite matrices to small matrices and vice versa

Moh's user avatar

Moh

modified Nov 20 at 16:19

6 votes

2 answers

99 views

Intuition behind using $\pi$-system in Measure Theory

Michael Greinecker's user avatar

Michael Greinecker

35.4k

3 votes

3 answers

202 views

Simplify into reduced form

user21820's user avatar

user21820

61.3k

answered 10 hours ago

2 votes

3 answers

201 views

$f(x)$ is a cubic polynomial $f(k-1)f(k+1)<0$ is NOT true for any integer $k$. Find $f(8)$

T_T's user avatar

T_T

3,338

modified 11 hours ago

2 votes

2 answers

110 views

Is the isomorphism $(G/N_1)/(N_2/N_1)\cong G/N_2$ in the third isomorphism theorem actually an equality?

Shaun's user avatar

Shaun ♦

48.4k

2 votes

3 answers

213 views

Prove $AF, BC, GE$ are concurrent in a tangent–circumcircle configuration

D S's user avatar

D S

5,862

Noah Schweber's user avatar

3 votes

1 answer

195 views

Comparison of Dedekind-finite sets

Noah Schweber

264k

4 votes

1 answer

190 views

Is there a converse of the Copeland-Erdős theorem on normal numbers?

Jotazuma's user avatar

Jotazuma

4 votes

1 answer

188 views

Real variable method to show that $\int_{-\infty}^\infty \frac{\sinh ax}{\sinh \pi x}\cos bx dx = \frac{\sin a}{\cos a+\cosh b}$?

homo_morph's user avatar

homo_morph