• Yesterday, 22:53
I do not see any problem with defining the notion of an irreducible in an arbitrary ring. Though we may not get any nice theorems concerning...
1 replies | 45 view(s)
• Yesterday, 11:04
MarkFL replied to a thread Hi everyone! in Introductions
Hello and welcome to MHB, Raisa! (Wave)
3 replies | 69 view(s)
• Yesterday, 10:02
caffeinemachine replied to a thread Hi everyone! in Introductions
Hey Raisa! I am currently a PhD student in mathematics, but I was also a mechanical engineering undergrad before I switched to math. I would say that...
3 replies | 69 view(s)
• Yesterday, 03:13
Here is this week's POTW: ----- Find the exact value for the real root of the equation $x^3+3x-2=0$. ----- Remember to read the POTW...
0 replies | 51 view(s)
• Yesterday, 02:59
Congratulations to the following members for their correct solution::) 1. kaliprasad 2. lfdahl Honorable mention goes to cmath123, as he has his...
1 replies | 121 view(s)
• February 18th, 2017, 02:29
MarkFL replied to a thread 231.14.88 3d surface in Calculus
Multiplying through by $9+6x-8y$ and distributing the $26$, we obtain -x^2-y^2+z^2=156x-208y+234 -x^2-156x-y^2+208y+z^2=234 ...
3 replies | 54 view(s)
• February 15th, 2017, 20:29
You have two points on the graph, so you can compute the slope as follows: m=\frac{\Delta y}{\Delta x}=\frac{y_2-y_1}{x_2-x_1} Then, you can...
2 replies | 59 view(s)
• February 14th, 2017, 23:47
Yes, the derivative of the function evaluated at the $x$-coordinate of the tangent point will give you the slope $m$ of the tangent line. :)
4 replies | 92 view(s)
• February 14th, 2017, 23:18
The first derivative of a function gives you the slope of the tangent line, not the tangent line itself. Thus,for some function $f(x)$, the tangent...
4 replies | 92 view(s)
• February 14th, 2017, 22:17
Let's try your substitution of: u=x+9\implies du=dx I=\int_9^{18}\frac{(u-9)^3}{u^2}\,du By the binomial theorem: ...
1 replies | 47 view(s)
• February 14th, 2017, 12:31
Just to follow up, we left off with: 8-\frac{15000}{x}=5 Arrange as: 3=\frac{15000}{x} Multiply through by \frac{x}{3}\ne0:
2 replies | 101 view(s)
• February 12th, 2017, 22:44
Yes, those are typically how these two metrics for the center of the data are used. So it comes down to how do we define "having outliers"? In real...
7 replies | 151 view(s)
• February 12th, 2017, 00:21
Yes, we use $\LaTeX$ powered by MathJax, which is what you'll find on most other math sites. The only difference is, unlike other sites, we provide...
3 replies | 106 view(s)
• February 11th, 2017, 18:00
Jameson replied to a thread Election in Pre-Algebra and Algebra
Hi there. :) Look at the part in red to start with. This kind of issue comes up a lot with word problems. We know that the ratio of purple...
2 replies | 64 view(s)
• February 11th, 2017, 17:56
Hi rebo1984, What rules and guidelines have you been given to decide? In general I agree with your answers. The median is less sensitive to...
7 replies | 151 view(s)
• February 10th, 2017, 11:34
Let's generalize the method I posted >>>here<<< to reflect a given point $(a,b)$ about the line $y=mx+k$, where ($m\ne0$). We will call the reflected...
3 replies | 113 view(s)
• February 10th, 2017, 10:27
MarkFL replied to a thread Line y = (x/2) + 3 in Pre-Calculus
Another way to show 3 points are collinear is to pick two distinct pairs from the 3 points, and show that the slope between both pairs is the same. :D
2 replies | 61 view(s)
• February 10th, 2017, 00:30
MarkFL replied to a thread Square root Convergence in Calculus
To extend the ladder for $\sqrt{k}$, you want: x_{n+1}=x_n+y_n y_{n+1}=x_{n+1}+(k-1)x_n
1 replies | 74 view(s)
• February 9th, 2017, 15:50
Now necessarily...for example if we multiply through by $k$, we get: k+1=k^2 And BOOM! we have question 1 of part B) done.
12 replies | 193 view(s)
• February 9th, 2017, 12:36
Here is this week's POTW: ----- Given that $\sqrt{x^3+1648}-\sqrt{4949-x^3}=75$ for $x\in\Bbb{N}$. Find $x$. ----- Remember to read the...
1 replies | 121 view(s)
• February 9th, 2017, 12:26
No one answered last week's problem.(Sadface) You can find the suggested solution as follows: Let...
1 replies | 139 view(s)
• February 9th, 2017, 03:49
We don't need to solve for $y$. We need only to have shown that: \frac{x}{y}=\frac{1+\sqrt{5}}{2} to satisfy part A) of the problem. For part...
12 replies | 193 view(s)
• February 9th, 2017, 02:15
That's not quite right: x=\frac{-(-y)\pm\sqrt{(-y)^2-4(1)(-y^2)}}{2(1)}=y\frac{1\pm \sqrt{5}}{2} Discarding the negative root, we obtain: ...
12 replies | 193 view(s)
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### 28 Visitor Messages

1. Hello and welcome back to MHB, Fernando Revilla!

We are happy to see that you have returned, and we look forward to your continued participation here!

On Behalf Of MHB's Staff,

Jameson.
2. Hello and welcome back to MHB, Fernando Revilla!

We are happy to see that you have returned, and we look forward to your continued participation here!

On Behalf Of MHB's Staff,

Jameson.
3. Welcome back, Fernando! Glad to see you've rejoined the party!
4. Woow , it's been a while. Welcome back
5. Welcome back, Fernando!
6. Hey! There you are! I was wondering if you'd be back. We missed you!
7. Hey Fernando, nice to see you back!
8. Congratulations on the 500 post mark! It's great that you've been so active this year Looking forward to the next 500 posts.
9. hola profesor fernando que pena escribir en español pero no se ingles, queria saber si usted conoce alguna aplicacion de las integrales sin(x*x*x*x), he desarrollado un metodo numerico para calcularlas en cualquier valor comprendido en el intervalo de (4,infinito) y mi abogado me dice que tengo que encontrar una aplicacion para poder proteger y blindar de una forma mas segura los derechos de autor, estare pendiente de su respuesta, o si conoce a alguien que me pueda ayudar le agradeceria enormemente, gracias.

hello fernando teacher wanted to know if you know any application of the integral sin (x * x * x * x), I have developed a numerical method to calculate any value in the interval (4, infinity) and my lawyer tells me I have to find an application in order to protect and shield in a more secure copyright, I will be aware of your answer, or if you know someone who can help me I would appreciate greatly, thanks.

att
jefferson alexander vitola
10. LOL! Nicely put!
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#### Basic Information

Biography:
Prof. of Mathematical Methods, Univ. Alfonso X El Sabio, Madrid.
(Up until the 2008/2009 academic year. I am now devoted to investigation).
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