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active 44featured hot week month

100

votes

11

answers

5

kviews

A “simple” 3rd grade problem…or is it?

recreational-mathematics

13m ago Kaz 1,799

7

votes

16

answers

962

views

Why is $n^2-\frac{n^2}{2} =\frac{n^2}{2}$? [closed]

homework algebra-precalculus powers

9h ago Calvin 1

14

votes

5

answers

701

views

Intervals that are free of primes

number-theory elementary-number-theory analytic-number-theory

2d ago P.. 8,561

20

votes

7

answers

1

kviews

Does $\frac{x}{x}=1$ when $x=\infty$?

calculus

apr 29 at 21:43 Stahl 3,180

10

votes

10

answers

657

views

What is the point of countable vs. uncountable sets?

analysis

2d ago Hurkyl 20.6k

18

votes

6

answers

608

views

Why is $\frac{1}{\frac{1}{0}}$ undefined?

algebra-precalculus

apr 29 at 22:36 Alfe 111

26

votes

6

answers

473

views

Is $\sqrt[3]{p+q\sqrt{3}}+\sqrt[3]{p-q\sqrt{3}}=n$, $(p,q,n)\in\mathbb{N} ^3$ solvable?

algebra-precalculus number-theory elementary-number-theory diophantine-equations

apr 30 at 10:31 Américo Tavares 20.1k

8

votes

4

answers

493

views

Divisibility by 3?

elementary-number-theory

apr 28 at 17:52 Peter Phipps 1,305

14

votes

5

answers

244

views

Convergent or Divergent? $\sum_{n=1}^\infty\left(2^{\frac1{n}}-1\right)$

sequences-and-series convergence

apr 27 at 8:21 hkBattousai 671

9

votes

6

answers

218

views

Evaluate $ \lim_{x \to 0} \frac{x^2}{x+\sin (\frac 1 x)} $

limit

11h ago robjohn♦ 56.7k

7

votes

5

answers

337

views

Solve $\dfrac{1}{1+\frac{1}{1+\ddots}}$

homework continued-fractions

2d ago user3490 123

16

votes

5

answers

339

views

limit of : $a_{n+2} =\frac{1}{a_n} + \frac{1}{a_{n+1}}$

real-analysis sequences-and-series limit recurrence-relations

apr 30 at 14:20 YKall 401

5

votes

5

answers

311

views

How is this proof flawed?

exponentiation powers fake-proofs

apr 29 at 16:08 Antonio Vargas 6,450

6

votes

5

answers

226

views

Why is $\sqrt{4} = 2$ and Not $\pm 2$? [duplicate]

algebra-precalculus

5h ago CommonerG 300

10

votes

8

answers

218

views

Limit of $\frac{\log(n!)}{n\log(n)}$ as $n\to\infty$.

calculus limit asymptotics

2d ago marty cohen 5,449

8

votes

5

answers

332

views

Finding the smallest integer $n$ such that $1+1/2+1/3+…+1/n≥9$?

combinatorics sequences-and-series

apr 28 at 19:48 Kamal 154

9

votes

5

answers

243

views

What is the canonical definition of an open set?

general-topology elementary-set-theory

1d ago Stefan H. 1,495

12

votes

4

answers

322

views

the sixth number system

number-systems

apr 30 at 6:16 Pieter Geerkens 181

10

votes

1

answer

311

views

Does $f(x) = f(2x)$ for all real $x$, imply that $f(x)$ is a constant function?

calculus functions functional-equations

apr 27 at 18:18 Crocodile 560

4

votes

5

answers

182

views

Prove that if $A - A^2 = I$ then $A$ has no real eigenvalues

linear-algebra

2d ago Manuel Eberl 211

10

votes

4

answers

217

views

What does it mean for a set to exist?

elementary-set-theory soft-question philosophy

2d ago Dan Christensen 1,496

9

votes

4

answers

153

views

a sequence $\{s_n\}$ with $\sum s_n$ convergent

real-analysis sequences-and-series

20h ago Aryabhata 46.9k

2

votes

5

answers

319

views

The hypotenuse of a right angle triangle measures 12 cm. What size angles would produce maximum…

trigonometry derivatives

1d ago Kaster 2,883

7

votes

3

answers

155

views

If $G$ has only 2 proper, non-trivial subgroups then $G$ is cyclic

group-theory finite-groups

1d ago Sugata Adhya 1,428

2

votes

5

answers

147

views

Looking for a function with $f(0) = 0$, $f'(0) = 1$ and $\lim\limits_{x\to\infty}f(x)=1$

functions

1d ago Robert Mastragostino 7,484

5

votes

4

answers

238

views

Differentiating $\;y = x a^x$

calculus derivatives

apr 30 at 15:55 TMM 6,588

6

votes

6

answers

170

views

Representing the function $\mathbb Z_9\to\mathbb Z_9$, $f(0) = 1$, $f(1) = \ldots = f(8) = 0$ as a polynomial in $\mathbb Z_9[x]$

number-theory elementary-number-theory functions polynomials

apr 30 at 18:21 Jyrki Lahtonen 29.6k

1

vote

6

answers

278

views

Is a Quadratic equation a function?

quadratics

apr 29 at 19:53 Kaz 1,799

12

votes

3

answers

229

views

Application of Liouville's Theorem

complex-analysis

2d ago user75064 550

11

votes

3

answers

158

views

What is necessary to exchange messages between aliens?

logic computer-science cryptography information-theory

apr 28 at 5:47 julian fernandez 1,502

8

votes

4

answers

136

views

Binomial Theorem Identities

combinatorics binomial-coefficients

apr 27 at 7:07 Adi Dani 5,706

3

votes

4

answers

134

views

$2^n$ subsets of set with $n$ elements $\overset{?}{\implies}$ $\mathbb{R}$ has $2^\infty=\infty$ subsets

elementary-set-theory

apr 29 at 8:06 Asaf Karagila 87.1k

8

votes

2

answers

165

views

Factoring x + y

functional-equations

1d ago Peter Tamaroff 24.5k

7

votes

3

answers

141

views

Asymptotic for the integral involving exponential

integral asymptotics

apr 30 at 1:01 Mhenni Benghorbal 12.3k

8

votes

3

answers

165

views

Solve $x^3+x \equiv 1 \pmod p$

number-theory algebraic-number-theory finite-fields

1d ago Matt E 55.6k

1

vote

6

answers

156

views

Integral Question - $\int\frac{1}{x^2-6x}\,\mathrm dx$

homework calculus integral

2d ago Tharsis 629

3

votes

6

answers

121

views

Solve for $x$: question on logarithms.

logarithms

23h ago Kaz 1,799

4

votes

4

answers

89

views

Finding a continuous function $f: \mathbb{R} \to \mathbb{R}$ such that $f(\mathbb{R})$ is neither open nor closed

homework analysis

1h ago P.. 8,561

7

votes

3

answers

240

views

Why is 1 raised to infinity Not defined and not “1” [duplicate]

soft-question education exponentiation

2d ago Ruluk 21

3

votes

5

answers

114

views

Revisted: GCD - $(a,c)=1=(b,c) \overset{?}{\implies} (ab,c)$

number-theory elementary-number-theory

1d ago Alyosha 930

2

votes

3

answers

98

views

Example of topological space $(X,\tau)$ is Hausdorff but not discrete.

general-topology examples-counterexamples

2d ago MJD 19.9k

4

votes

2

answers

113

views

Let $m^n-1$ be prime. What can $m$ be?

prime-numbers

2d ago vonbrand 5,669

3

votes

3

answers

73

views

How to show if $|a_{n+1} - a_{n}| \le \frac{1}{2^n}$ then the sequence is Cauchy.

homework real-analysis

apr 30 at 1:48 i.a.m 1,368

7

votes

3

answers

85

views

Find the limit of $ x_n = \prod_{j=2}^{n} \left(1 - \frac{2}{j(j+1)}\right)^2$

sequences-and-series limit

10h ago robjohn♦ 56.7k

11

votes

1

answer

134

views

What groups can G/Z(G) be?

group-theory finite-groups

apr 28 at 0:00 user2245944 58

2

votes

6

answers

79

views

Finding the remainder when $2^{100}+3^{100}+4^{100}+5^{100}$ is divided by $7$

elementary-number-theory modular-arithmetic

apr 30 at 19:28 Lee Sleek 51

5

votes

2

answers

99

views

Seeing that $\Bbb F_2[x]/(x^2+x+1)$ is a field

ring-theory finite-fields

apr 30 at 16:34 rschwieb 19.5k

5

votes

4

answers

119

views

matrices $A$ of order $2 \times 2$ that satisfy the equation $A^2-5A+6I = O$

homework matrices

1d ago Graham Hesketh 160

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