User user402326

5 votes

1 answer

548 views

How many ways to arrange $2n$ people in two lines

asked Oct 16, 2017 at 23:45

5 votes

1 answer

1k views

Classical Gram-Schmidt for matrix $A$

asked Sep 29, 2018 at 23:01

4 votes

2 answers

198 views

How to quickly solve $y=\int_{-\pi/4 }^{\pi/4 } \left[\cos x + \sqrt{1+x^2}\sin^3x\cos^3x\right]dx$?

asked Dec 28, 2016 at 0:29

4 votes

1 answer

2k views

Proving that the tent map is topologically conjugate to the quadratic map

asked Mar 7, 2017 at 5:20

3 votes

2 answers

86 views

show that $\left(\sum_{i=0}^\infty\frac{a^i}{i!}\right)\left(\sum_{j=0}^\infty\frac{b^j}{j!}\right) = \sum_{k=0}^\infty\frac{(a+b)^k}{k!}$

asked Oct 10, 2017 at 20:29

2 votes

2 answers

407 views

Solving this non-homogenous recurrence relation

asked Oct 12, 2017 at 12:10

2 votes

5 answers

1k views

Compute $\sum_{k=1}^n \binom nk k 3^k$

asked Sep 27, 2017 at 12:14

2 votes

1 answer

470 views

Compute $\int_0^2 x^3 d[x]$ using Riemann–Stieltjes

asked Nov 29, 2017 at 15:41

2 votes

1 answer

2k views

Bounded sequence implies existence of $\lim\sup$ and $\lim\inf$

asked Sep 18, 2017 at 21:18

2 votes

2 answers

1k views

What is a two parameter family of matrices?

asked Oct 3, 2018 at 3:15

2 votes

2 answers

1k views

Show that $\sqrt{x^TQx+1}$ is convex for positive definite $Q$

asked Oct 31, 2019 at 19:31

1 vote

0 answers

23 views

$x$ is orthogonal to $v_j$ ($j=1,\dots,r$) iff $x\in\text{span}\{v_{r+1},\dots,v_{n}\}$

asked Sep 13, 2018 at 19:25

1 vote

3 answers

4k views

How many flags, with 3 horizontal stripes, can be made if two stripes are one color and the third is a different color?

asked Sep 6, 2017 at 9:08

1 vote

0 answers

39 views

Let $a_n >0$ and $\lim\inf a_n =0$, show that infinitely many $n$ exist such that $a_n < \min\{a_1,...,a_{n-1}\}$

asked Oct 17, 2017 at 18:16

1 vote

2 answers

121 views

Using pigeonhole to prove/disprove a certain number of consecutive vists

asked Nov 9, 2017 at 10:59

1 vote

2 answers

314 views

Recurrence relation for the number of codewords of length $n$ from {0, 1, 2} with no two $0$’s appearing consecutively

asked Oct 4, 2017 at 17:30

1 vote

2 answers

122 views

Number of ways for a 6 digit license plate such that each digit is unique except for one

asked Oct 16, 2017 at 15:00

0 votes

1 answer

2k views

Show that $S(n, n-2) = {n\choose3} + 3{n\choose4}$

asked Sep 17, 2017 at 10:28

0 votes

1 answer

55 views

If we have $n$ different kinds of objects...

asked Sep 19, 2017 at 20:31

0 votes

1 answer

345 views

Using generating functions to find number of ways to divide 15 indistinguishable balls into 10 distinguishable non empty cells?

asked Sep 23, 2017 at 21:12

0 votes

0 answers

55 views

Prove that for each positive integer $n$, $R^n$ and $I^n$ are simply connected

asked Apr 21, 2017 at 6:46

0 votes

0 answers

63 views

Why do we have $|f(x)-f(p)|\leq A|x-p|$ and not $|f(x)-f(p)|< A|x-p|$?

asked Jan 24, 2017 at 21:42

0 votes

1 answer

438 views

Showing that the generalized inverse for a square invertible matrix is unique

asked Oct 2, 2018 at 4:10

-1 votes

1 answer

43 views

Show that $\sum_{k=1}^n e^{2\pi i (k-1)(a-b)/n}=0$

asked Sep 10, 2018 at 4:28

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24 Questions

How many ways to arrange $2n$ people in two lines

Classical Gram-Schmidt for matrix $A$

How to quickly solve $y=\int_{-\pi/4 }^{\pi/4 } \left[\cos x + \sqrt{1+x^2}\sin^3x\cos^3x\right]dx$?

Proving that the tent map is topologically conjugate to the quadratic map

show that $\left(\sum_{i=0}^\infty\frac{a^i}{i!}\right)\left(\sum_{j=0}^\infty\frac{b^j}{j!}\right) = \sum_{k=0}^\infty\frac{(a+b)^k}{k!}$

Solving this non-homogenous recurrence relation

Compute $\sum_{k=1}^n \binom nk k 3^k$

Compute $\int_0^2 x^3 d[x]$ using Riemann–Stieltjes

Bounded sequence implies existence of $\lim\sup$ and $\lim\inf$

What is a two parameter family of matrices?

Show that $\sqrt{x^TQx+1}$ is convex for positive definite $Q$

$x$ is orthogonal to $v_j$ ($j=1,\dots,r$) iff $x\in\text{span}\{v_{r+1},\dots,v_{n}\}$

How many flags, with 3 horizontal stripes, can be made if two stripes are one color and the third is a different color?

Let $a_n >0$ and $\lim\inf a_n =0$, show that infinitely many $n$ exist such that $a_n < \min\{a_1,...,a_{n-1}\}$

Using pigeonhole to prove/disprove a certain number of consecutive vists

Recurrence relation for the number of codewords of length $n$ from {0, 1, 2} with no two $0$’s appearing consecutively

Number of ways for a 6 digit license plate such that each digit is unique except for one

Show that $S(n, n-2) = {n\choose3} + 3{n\choose4}$

If we have $n$ different kinds of objects...

Using generating functions to find number of ways to divide 15 indistinguishable balls into 10 distinguishable non empty cells?

Prove that for each positive integer $n$, $R^n$ and $I^n$ are simply connected

Why do we have $|f(x)-f(p)|\leq A|x-p|$ and not $|f(x)-f(p)|< A|x-p|$?

Showing that the generalized inverse for a square invertible matrix is unique

Show that $\sum_{k=1}^n e^{2\pi i (k-1)(a-b)/n}=0$