Question

There exists $x \in \mathbb{R}$ such that the number $f(x)=x^2 +5x +4$ is prime."

score 125 · Answer 1 · 2026-04-14 02:22:17

125

Views

There exists $x \in \mathbb{R}$ such that the number $f(x)=x^2 +5x +4$ is prime."

Published on 14 Apr 2026 - 2:22

score 52 · Answer 2 · 2026-04-14 07:34:34

52

Views

Steinhauss theorem and sums of sets

Published on 14 Apr 2026 - 7:34

score 69 · Answer 3 · 2026-04-16 05:15:26

69

Views

How to prove if $C \subseteq B$ then $A - B \subseteq A-C$

Published on 16 Apr 2026 - 5:15

score 2.3k · Answer 4 · 2026-04-09 18:09:54

2.3k

Views

How to prove $\sqrt{18}$ is irrational without using proof by contradiction?

Published on 09 Apr 2026 - 18:09

score 1.1k · Answer 5 · 2026-05-11 10:11:56

1.1k

Views

Prove that the maximum number of knights that can be placed on a chess board NxN such that no knight attacks another is n^2/2

Published on 11 May 2026 - 10:11

score 44 · Answer 6 · 2026-04-13 17:45:08

Why does by choosing an element $m\ne n+1: f(a_0) = m$ not guarantee immediately a bijective function between $A-\{a_0\} \mapsto S_{n+1}$?

score 53 · Answer 7 · 2026-05-11 04:37:08

53

Views

Kripke models - prove that formula is not tautology in intuitionistical logic

Published on 11 May 2026 - 4:37

score 570 · Answer 8 · 2026-04-15 21:27:46

570

Views

Why does the Hausdorff distance between $I=[0,1]$ and $B_n = \{0, \frac{1}{n}, \cdots, \frac{n-1}{n}, 1\}$ tend to zero?

Published on 15 Apr 2026 - 21:27

score 7.1k · Answer 9 · 2026-04-17 09:04:19

7.1k

Views

Prove that $a^{\ln{(b)}} = b^{\ln{(a)}}$

Published on 17 Apr 2026 - 9:04

score 996 · Answer 10 · 2026-04-09 10:06:13

996

Views

Understanding an example of continuous functions with divergent Fourier series at a point on the circle

Published on 09 Apr 2026 - 10:06

score 69 · Answer 11 · 2026-04-17 14:34:19

69

Views

Prove rigorously in arbitrary metric spaces that $\lim_{x \to a} \phi (x) + \gamma (x) = \lim_{x \to a} \phi (x) + \lim_{x \to a} \gamma(x)$

Published on 17 Apr 2026 - 14:34

score 92 · Answer 12 · 2026-05-11 07:50:21

92

Views

Bolyai's statement in "the Science of absolute space " paragraph 9

Published on 11 May 2026 - 7:50

score 332 · Answer 13 · 2026-04-14 16:57:48

332

Views

If $f$ and $g$ are continuous in an arbitrary metric space $X$, show that $f + g$ is also continuous

Published on 14 Apr 2026 - 16:57

score 57 · Answer 14 · 2026-04-11 20:10:45

57

Views

How to prove $(A - B) - C \subseteq A - (B - C)$

Published on 11 Apr 2026 - 20:10

score 139 · Answer 15 · 2026-04-16 00:19:18

139

Views

Explain how $(p \land \lnot q) \iff (\lnot p \lor q)$

Published on 16 Apr 2026 - 0:19

List Question

There exists $x \in \mathbb{R}$ such that the number $f(x)=x^2 +5x +4$ is prime."

Steinhauss theorem and sums of sets

How to prove if $C \subseteq B$ then $A - B \subseteq A-C$

How to prove $\sqrt{18}$ is irrational without using proof by contradiction?

Prove that the maximum number of knights that can be placed on a chess board NxN such that no knight attacks another is n^2/2

Why does by choosing an element $m\ne n+1: f(a_0) = m$ not guarantee immediately a bijective function between $A-\{a_0\} \mapsto S_{n+1}$?

Kripke models - prove that formula is not tautology in intuitionistical logic

Why does the Hausdorff distance between $I=[0,1]$ and $B_n = \{0, \frac{1}{n}, \cdots, \frac{n-1}{n}, 1\}$ tend to zero?

Prove that $a^{\ln{(b)}} = b^{\ln{(a)}}$

Understanding an example of continuous functions with divergent Fourier series at a point on the circle

Prove rigorously in arbitrary metric spaces that $\lim_{x \to a} \phi (x) + \gamma (x) = \lim_{x \to a} \phi (x) + \lim_{x \to a} \gamma(x)$

Bolyai's statement in "the Science of absolute space " paragraph 9

If $f$ and $g$ are continuous in an arbitrary metric space $X$, show that $f + g$ is also continuous

How to prove $(A - B) - C \subseteq A - (B - C)$

Explain how $(p \land \lnot q) \iff (\lnot p \lor q)$

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