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  1. M

    How to post a matrix?

    Thanks a lot, really helped!
  2. M

    System of linear equations

    Ok, so for the first one there's no way I can find m so the system will have infinitely many solutions? Edit: For the second, I did the following: 1. multiplied the first line by -2 and added to the second; 2. multiplied the second line by \frac{1}{k-4} So I got: x + 2y + kz = 1 0x +...
  3. M

    System of linear equations

    Well, I know that if det A = 0 means the two slopes are equal, but they can be parallel or identical. I want them to be identical so the system will have infinitely many solutions. I have the following equations: y = 4 - \frac{m}{3}x y = 10 - 4x For the slopes to be identical...
  4. M

    System of linear equations

    Ok, let me see if I'm doing right. For the first one let A be the coeficient matrix: A = \left(\begin{array}{cc}m&3\\2&\frac{1}{2}\end{array}\right) so det(A) = \frac{m}{2} - 6 Ax = \left(\begin{array}{cc}m&12\\2&5\end{array}\right) and Ay =...
  5. M

    How to post a matrix?

    I see. But if I post it'll be ok, right? Thanks!
  6. M

    How to post a matrix?

    Hello, I've been trying to use LaTeX to post a matrix but didn't succeed. Here's the code I have: A = \left(\begin{array}{cc}m&3\\2&1/2\end{array}\right) But when I put it between [ tex ][ /tex ] (without spaces) I get a '=>'. But here it's working, see A =...
  7. M

    System of linear equations

    Homework Statement Exercise 1: For what value of m will the following system of linear equations have infinitely many solutions? mx + 3y = 12 2x + (1/2)y = 5 Exercise 2: For what value of k will the following system of linear equations x + 2y + kz = 1 2x + ky + 8z = 3 have a) unique...
  8. M

    Linear Algebra - Linear Spaces

    Thanks a lot for the fast reply!
  9. M

    Linear Algebra - Linear Spaces

    Hello there, I'm having some problems with a proof-like exercise on linear algebra. Here's what I'm supposed to do: Homework Statement Determine whether each of the given sets is a real linear space, if addition and multiplication by real scalars are defined in the usual way. For those...
  10. M

    Condition for differentiability

    Now I got it! Thanks a lot everyone for your help!
  11. M

    Condition for differentiability

    Sorry, I misspelled the word. df/dx = 2 and df/dy = -1, and they are continuous in R²... right?
  12. M

    Condition for differentiability

    Perhaps I figured that out for the second one: I should find the partial derivative of the function using limits when x and y tend to 0? Yet the first one isn't very clear to me...
  13. M

    Condition for differentiability

    But how can I find this (x_0, y_0) when the exercise asks if its differentiable in R²? For the second function, I can also say that the domain is all the circunferences with a radius bigger than 0... does it helps in anything? Thanks.
  14. M

    Condition for differentiability

    For the first one, the domain is R², right? And for the second, as there is no log of numbers equal or below zero, we have that x²+y²>0. Isn't that right? The teacher told us to use a certain book to study, but this is not there... Thanks again.
  15. M

    Condition for differentiability

    Uhmmm the question is: "Verify if each function is differentiable at the points of its domain." a)f(x,y) = 2x - y b)f(x,y) = ln(2x²+3y²)
  16. M

    Condition for differentiability

    What you mean by "total differentiability"? I thought that when derivating a function with multiple variables I should diferentiate it for x and then for y. For a function of one argument to be differentiable it needs to be countinous in its domain?
  17. M

    Sugestion for a Electrical energy generation project

    You guys helped a lot! I'll talk to my mate so we can decide which one we are going to do and start tomorrow. Thanks a lot all of you!
  18. M

    Condition for differentiability

    What's the condition for f(x,y) to be differentiable in its domain? I googled for it but couln't find... Thanks in advance.
  19. M

    Sugestion for a Electrical energy generation project

    I see. I googled for it and found this: http://www-mtl.mit.edu/~anantha/docs/journals/2001_meninger_vlsi.pdf [Broken] But it talks about that MEMS technology, which I'm not familiar with. Is that expensive? Because we are supposed to create a low-cost engine. Can I do it without spending...
  20. M

    Sugestion for a Electrical energy generation project

    That's a nice idea... but I think we are going to be evaluated separately... I heard something about using plants, do you lnow this way? The professor said nothing about the scale, but I think that if we can light up a lamp it's enough. What is "omnidirectional acceleration"? I know the...
  21. M

    Sugestion for a Electrical energy generation project

    Hello there, I'm new in this forum so sorry if this is not the right session to post my question. Well I'm taking a subject called Energy: Origins, Conversion and Uses (I guess this is the correct translation) and I need to do a final project which requires me to generate electrical...
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