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GeoffDS
  • Member for 13 years, 1 month
  • Last seen more than 1 year ago
63 votes
Accepted

Math and mental fatigue

48 votes
Accepted

Is Sage on the same level as Mathematica or Matlab for graph theory and graph visualization?

44 votes

Show that the set of all finite subsets of $\mathbb{N}$ is countable.

35 votes

Can I use my powers for good?

33 votes
Accepted

Why is the expected value $E(X^2) \neq E(X)^2$?

27 votes

Theorems with an extraordinary exception or a small number of sporadic exceptions

23 votes
Accepted

Why is -10 smaller than -100?

22 votes

Books to study for Math GRE, self-study, have some time.

21 votes
Accepted

GRE Math Subject Test

18 votes

Why is the last digit of $n^5$ equal to the last digit of $n$?

17 votes

How to show that $f(x)=x^2$ is continuous at $x=1$?

16 votes

Deleting any digit yields a prime... is there a name for this?

13 votes

Determine $\lim_{x \to 0}{\frac{x-\sin{x}}{x^3}}=\frac{1}{6}$, without L'Hospital or Taylor

13 votes

Number of consecutive zeros at the end of $11^{100} - 1$.

12 votes

List of interesting integrals for early calculus students

12 votes
Accepted

Why is $\int^\infty_{-\infty} \frac{x}{x^2+1} dx$ not zero?

12 votes
Accepted

No closed form for the partial sum of ${n\choose k}$ for $k \le K$?

11 votes

Solve $e^x+x=1$

11 votes

Why does the series $\sum_{n=1}^\infty\frac{(-1)^{n-1}n!}{10^n}$ not converge?

10 votes

Theorems with an extraordinary exception or a small number of sporadic exceptions

10 votes

Preparation for Putnam?

10 votes
Accepted

How many non-isomorphic graphs with n vertices and m edges are there?

10 votes

Why $ac=b^2$ forces $a,c$ to be squares if $a,c$ are coprime?

9 votes
Accepted

How to compute a linear fractional transformation that maps a circle to a given circle?

8 votes

General Introduction to Functional and other Mathematic Notations

8 votes
Accepted

Rules of Division

8 votes
Accepted

How to calclulate multiplicative inverse of e mod $\phi(n)$?

8 votes
Accepted

Are Toeplitz matrices always square?

8 votes

Is the function $y=\ln x^2$ the same as $y=2\ln |x|$?

8 votes
Accepted

$\lim_{n\to\infty}\frac{a_{n-1}}{a_{n}}$

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