User zwim - Mathematics Stack Exchange

18 votes

Accepted

Derivative of $(x-1)(x-2)(x-3) \cdots (x-10)$ at $x=6$

answered Oct 6, 2017 at 18:22

12 votes

Intuition behind $\zeta(-1)$ = $\frac{-1}{12}$

answered Jan 6, 2017 at 12:45

12 votes

What is the name of this hexagon/pentagon polyhedron?

answered May 1, 2019 at 12:48

11 votes

Accepted

If $A$ and $B$ are invertible matrices, is $A+B$ invertible too?

answered Nov 28, 2017 at 19:37

11 votes

The sum of 8 consecutive Fibonacci numbers is not a Fibonacci number

answered Dec 1, 2017 at 18:48

10 votes

Accepted

Why is this proof incorrect? (limit product is product of the limits)

answered Sep 10, 2017 at 12:05

10 votes

How to explain to my daughter that $\frac {2}{3}$ is greater than $\frac {3}{5}$?

answered Apr 12, 2017 at 22:57

10 votes

Accepted

What is $\int_0^{\pi/2}\sin^7(\theta)\cos^5(\theta)d\theta$

answered Jan 6, 2019 at 18:10

9 votes

Find the power of the matrix.

answered Mar 20, 2022 at 16:41

8 votes

Prove that the golden ratio is irrational by contradiction

answered Sep 13, 2017 at 21:38

8 votes

Accepted

How to solve a system of linear equations modulo n?

answered Dec 7, 2017 at 21:18

7 votes

Is the empty set compact in $\mathbb R$?

answered Sep 14, 2020 at 11:17

7 votes

Rules for modulus and multiplication

answered Sep 4, 2017 at 7:12

7 votes

Accepted

Name this object derived from the Rhombicuboctahedron...

answered May 29, 2017 at 14:08

7 votes

A Particular Two-Variable System in a Group

answered Feb 18, 2017 at 23:18

7 votes

Determine if this series converges or diverges

answered Mar 16, 2017 at 7:00

6 votes

Accepted

Let $f: [a, +\infty [\to \mathbb{R}$ derivable such that $\lim_{x\to+\infty} xf'(x) = k> 0$. Prove that $\lim_{x\to+\infty} f(x)=+ \infty$.

answered Apr 20, 2021 at 17:50

6 votes

if p is prime then 1920 divides $p^4-10p^2+9$

answered Apr 23, 2021 at 7:40

6 votes

Accepted

Finding the value of $\sqrt[4]{(4+\sqrt7)^{-1}}\sqrt{1+\sqrt7}$ with other approaches

answered Jul 6, 2022 at 9:45

6 votes

Accepted

Polynomial system of equations over integers

answered Jul 30, 2023 at 15:54

6 votes

How many resistors are needed?

answered Mar 30, 2017 at 13:34

6 votes

Accepted

Can indefinite double integrals be solved by change of variables technique?

answered Feb 8, 2017 at 4:09

6 votes

Accepted

Coercive continuous function on a closed subset has a global minimum proof

answered Apr 18, 2017 at 16:12

6 votes

Proving it has all real roots

answered May 11, 2017 at 6:04

6 votes

What formula to chose a nonlinear formula?

answered May 15, 2019 at 21:59

6 votes

How to multiply on a calculator which only allows add, subtract and reciprocal

answered Jan 28, 2018 at 12:51

6 votes

Which solution to the integral $\int \frac {dx}{x \sqrt {x^2-1}}$ is correct and why?

answered Mar 27, 2020 at 23:40

5 votes

Is there $C$ such that $ \int_a^\infty \frac{1}{b^2 + x^2} dx \leq \frac{C}{a+b} $ for all $a,b>0$?

answered Aug 11, 2023 at 21:36

5 votes

Accepted

Explanation on the non existence of this limit

answered Jan 8 at 16:19

5 votes

remarkable identity for complex numbers

answered Oct 22, 2022 at 11:01

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1,630 Answers

Derivative of $(x-1)(x-2)(x-3) \cdots (x-10)$ at $x=6$

Intuition behind $\zeta(-1)$ = $\frac{-1}{12}$

What is the name of this hexagon/pentagon polyhedron?

If $A$ and $B$ are invertible matrices, is $A+B$ invertible too?

The sum of 8 consecutive Fibonacci numbers is not a Fibonacci number

Why is this proof incorrect? (limit product is product of the limits)

How to explain to my daughter that $\frac {2}{3}$ is greater than $\frac {3}{5}$?

What is $\int_0^{\pi/2}\sin^7(\theta)\cos^5(\theta)d\theta$

Find the power of the matrix.

Prove that the golden ratio is irrational by contradiction

How to solve a system of linear equations modulo n?

Is the empty set compact in $\mathbb R$?

Rules for modulus and multiplication

Name this object derived from the Rhombicuboctahedron...

A Particular Two-Variable System in a Group

Determine if this series converges or diverges

Let $f: [a, +\infty [\to \mathbb{R}$ derivable such that $\lim_{x\to+\infty} xf'(x) = k> 0$. Prove that $\lim_{x\to+\infty} f(x)=+ \infty$.

if p is prime then 1920 divides $p^4-10p^2+9$

Finding the value of $\sqrt[4]{(4+\sqrt7)^{-1}}\sqrt{1+\sqrt7}$ with other approaches

Polynomial system of equations over integers

How many resistors are needed?

Can indefinite double integrals be solved by change of variables technique?

Coercive continuous function on a closed subset has a global minimum proof

Proving it has all real roots

What formula to chose a nonlinear formula?

How to multiply on a calculator which only allows add, subtract and reciprocal

Which solution to the integral $\int \frac {dx}{x \sqrt {x^2-1}}$ is correct and why?

Is there $C$ such that $ \int_a^\infty \frac{1}{b^2 + x^2} dx \leq \frac{C}{a+b} $ for all $a,b>0$?

Explanation on the non existence of this limit

remarkable identity for complex numbers