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dmtri
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20 votes

How is possible that those shapes are equivalent in topology?

11 votes

Why does a polynomial with real, simple roots change its sign between its roots?

3 votes

Prove that the function $f: \mathbb{Z}\times \mathbb{Z}\to \mathbb{Z}\times \mathbb{Z}$ defined by $f(m,n) = (2m+3n,3m+2n)$ is not onto

3 votes
Accepted

Constant in front of the characteristic polynomial of a matrix

3 votes

Limit verification

3 votes

Prove/disprove: $f+g$ and $f$ are differentiable at $x_0$ $\implies$ $g$ is differentiable at $x_0$

3 votes

Prove that an open interval (0,1) and a closed interval [0,1] are not homeomorphic.

2 votes

Proving that $\{0,1\}^\mathbb N$ and $\mathbb{N^N}$ have the same cardinality

2 votes

Prove $\operatorname{span}\{ v_1,v_2,v_3 \} = \operatorname{span}\{u_1,u_2,u_3\} $

2 votes

How to show that a complexoid set is open

2 votes

Find $\lim\limits_{x \to\infty} (\frac {2+3x}{2x+1})^{x+1}$ without L'Hopital

2 votes

Is the sequence $a_{n} = 1 + \frac14 + \frac{2^2}{4^2} + \cdots +\frac{n^2}{4^n}$ Cauchy?

2 votes

I’m attempting to verify a limited relationship one of my high school students observed.

2 votes

why is the intersection of two sets with no common element equal to the subset containing the empty set and not simply the empty set?

2 votes

What exactly is a domain?

2 votes
Accepted

Is sum of square root and cube root always irracional?

2 votes
Accepted

Do absolute maxima and minima exist in this question?

2 votes

Is $f(x)=(\sin (1/x))^4$ Riemann integrable on $(0,1]$?

2 votes

Nearest point of the vertices of a triangle

2 votes

To prove the given inequality of n numbers

2 votes

Prove $d(f,g)= \min {|f(x)-g(x)}|$ in $C[a,b]$ is not metric

2 votes

If function has an absolute maximum at interior point, then it it not injective

1 vote

Is it true that $s_{n+1} - s_n \to 0$ in a convergent sequence?

1 vote
Accepted

Show that $\{(x,y): 0 < x \leq 1; y = \sin{1/x}\} \cup \{z: x = 0; -1 \leq y \leq 1\}$ is not path connected

1 vote

Largest possible value for a math test

1 vote

The number of distinct pairs of integers $(m,n)$ satisfying $|1+mn|<| m+n|<5$ is?

1 vote

Error In Wade's Analysis (continuous function preserves compactness)

1 vote
Accepted

Find all possible sums of a rows of a matrix

1 vote

Proof: Rank of block of matrix is smaller than rank of matrix

1 vote

Equivalent statement about a regular curve which is a part of a straight line.