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SescoMath's user avatar
SescoMath's user avatar
SescoMath
  • Member for 7 years, 1 month
  • Last seen this week
  • Berkeley
10 votes
Accepted

If $T_n = \{\frac{a}{n} \mid a \in \mathbb{Z}\}$, then what are $\bigcup_{n\in\mathbb{N}}T_n$ and $\bigcap_{n\in\mathbb{N}}T_n$?

6 votes

Open subsets of the space of linear operators

5 votes

Show that $ A − A^2$ is invertible given $A$'s eigenvalues?

4 votes

From digits {0, 1, 2, 3, 4, 5, 6}, how many four-digit even numbers with distinct digits can be constructed?

3 votes
Accepted

Is k=$\sqrt{6+\sqrt{6+...}}$ monotonically increasing?

3 votes
Accepted

Evaluating $\lim_\limits{x\to 3}\left(\frac{\left(x!-2x\right)}{x-3}\right)$

3 votes
Accepted

Prove that the value of $\Delta$ is an integer for the given determinant

2 votes
Accepted

Let $ G $ be a connected graph and $ C $ be an odd-length cycle in G. Show that if $ H $ has a perfect matching, then $ G $ has a perfect matching .

2 votes
Accepted

Uniform convergence of $\sin(nx) \cdot\frac{x}{n} + x$

2 votes

What does it mean for a subset of a vector space to be equal to its span?

2 votes

Define a relation $\sim$ on $\mathbb{R}$ by the rule $x \sim y$ if $x - y \in \mathbb{Q}$. List 5 elements of the equivalence class $[\pi]$

2 votes
Accepted

Show ex$(n, H)\leq \left\lfloor\frac{n^2+n}{4}\right\rfloor$

2 votes

Is it necessary $A^TA =I$ if $AA^T=I$ where A is a square matrix?

2 votes
Accepted

How to pronounce the notation $\lim\limits_{x \to a^+} F(x, y) = F(a^+, y) = F(a, y)$

2 votes

Find the digit of the units for the number $(5)(7^{29})+(8)(9^{72})$

2 votes

Prove that every natural number >1 has a unique way of prime factorization

2 votes

What's the difference between the probability of the nth coin flip, vs. the probability of flipping all the coins and getting one outcome

2 votes

No three consecutive cells of the same color

1 vote

How to tell if a sequence is bounded/upper/lower/etc?

1 vote

How is 0 a limit point of $\{1/n\}_{n=1}^{\infty}$?

1 vote
Accepted

Conformal circles (A property of inversions)

1 vote

Inequalities from a residue theorem example

1 vote
Accepted

Quantum Harmonic Oscillator Ladder operator propertie

1 vote

Find an upper bound for nth derivative of a holomorphic function

1 vote

prove cyclotomic polynomial is a minimal polynomial

1 vote

Rank-Nullity Theorem with Null Space and Column Space

1 vote

$\delta(ax) = \frac{\delta(x)}{|a|}$, where does absolute value come from?

1 vote

Intersection / union of sets over R with epsilon

1 vote
Accepted

Prove $0 \lt \int_0^1 f(x)\sin(rx)\mathrm{d} x \le \frac{1}{n!}, r\in(0, \pi] $, $f(x) = \frac{x^n(1-x)^n}{n!}, x\in [0, 1]$

1 vote
Accepted

How i can prove that $x^2=x\cos(x)+\sin(x)$ has 2 real roots?