Dec
17
answered Algebra of the complex plane
Dec
12
comment Counterexample to Eisenstein criterion
@Git Gud: This question makes sense. if one removes condition "$p$ is prime" by "$p$ is an arbitrary integer" then the statement is wrong.
Dec
8
revised What is the opposite of this condition?
reformatting equations and changing symbols
Dec
7
answered What is the opposite of this condition?
Dec
5
comment Is $x^4+x+1$ irreducible in $\Bbb{Q}[x]$?
$f(5)=631$ is a prime so f(x) is irreducible. See math.stackexchange.com/questions/568094/…
Dec
5
comment Is $x^4+x+1$ irreducible in $\Bbb{Q}[x]$?
you should do this $\pmod 2$. Otherwise you have to investigate $(x^2+ax \pm 1)(x^2+bx \pm 1)$
Dec
5
comment How to find the minimum of $a+b+\sqrt{a^2+b^2}$
I think the angle at $0$ is $90^\circ$ and $Q$ is the intersection of that angle bisection in $0$ and a normal to $AB$ in $P$. But $|OE|+|OF|+|EF|=|OA|+|OB|+AB|$ is still unclear to me.
Dec
5
comment How to find the minimum of $a+b+\sqrt{a^2+b^2}$
I agree that the problem is: find a triangle with vertices $0,A,B$ such that $A \in y^+$, $B \in x^+$, $P(1,2) \in \overline{AB}$ and the circumference is minimal. But I do not understand the second picture: why is the angle at $0$ not $90^\circ$, how do you get the center $Q$ of the circle and why is $|OE|+|OF|+|EF|=|OA|+|OB|+AB|$
Nov
27
comment Can you construct a field with 6 elements?
yes, you are right. I did not see that they are the same group.
Nov
26
comment Can you construct a field with 6 elements?
Why is $\mathbb{Z}_6$ the only abelian group of order 6? What is with $\mathbb{Z}_2 \times \mathbb{Z}_3$. It is abelian but acyclic. Maybe there are other abelian groups of order $6$? There are no such groups but how to proof this? Your argument does not work if the order of $1$ is not $6$, so if the goup is not cyclic. Please add "@miracle173" to a response otherwise I will not get a notification.
Nov
26
comment $3+33+\dots+33\ldots3={10^{n+1}-9^n-10\over 27}$
if $n=2$ the RHS is $101/3$ which is not an integer.
Nov
26
comment Can you construct a field with 6 elements?
Why must $\langle F, +\rangle$ be a cyclic group?
Nov
26
revised What is the coefficient of the $x^3$ term in the expansion of $(x^2+x-5)^7$ (See details)?
correction of the calculation error
Nov
25
suggested suggested edit on What is the coefficient of the $x^3$ term in the expansion of $(x^2+x-5)^7$ (See details)?
Nov
24
comment Find $x$ such that $x+x^2+x^3=x^9-x^7$
$x^9-x^7-x^3-x^2-x=(x^3-x-1)(x^5+x^2+1)x$
Nov
24
comment Does L'Hôpital's work the other way?
-1 The question is not formulated well. L'Hôpital's rule does not say that this two limites are equal. It says they are equal if some preconditions are fulfilled. Also the limes of the undefinite integrals does not make sense.
Nov
23
comment Solving $(z+1)^5 = z^5$
Why follows $$ \pars{1 + {1 \over z_{n}}}^{5} = \expo{2n\pi\ic}\,,\qquad n = 1, 2, 3, 4 $$ from $$ \pars{1 + {1 \over z}}^{5} = 1 $$
Nov
21
comment Can any one tell me the books for power series?
A book is Abramuwitz & Stegun: Handbook of Mathematical Functions with Formulas, Graphs, and Mathematical Tables You can use WolframAlpha which is documented here. Look up wikipedia for square root. Note the comment of @André Nicolas
Nov
19
awarded  Citizen Patrol
Nov
16
comment Is $ n^2-14n+24 $ a prime number?
-1 because it is incomplete