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#1 Re: Help Me ! » Matrix calculations - for which values does a system of equations... » 2016-07-27 23:13:24
For everyone that helped: I have passed my exam!! 
Thank you very much. I only found it polite to come back to you with this.
#2 Re: Help Me ! » Maths Exam and no clue » 2016-07-27 23:12:18
For everyone that helped: I have passed my exam!! Thank you very much. I only found it polite to come back to you with this.
#3 Re: Help Me ! » Word problem differential equation » 2016-07-27 23:10:59
For everyone that helped: I have passed my exam!! Thank you very much. I only found it polite to come back to you with this.
#4 Re: Help Me ! » Matrix calculations - for which values does a system of equations... » 2016-05-29 23:59:00
Hi there. Yes, I needed about two pages as well for the algebra. But, the good and most important news: I found the same solution!!! Jippieh!!! Thank you so much!
#5 Re: Help Me ! » Matrix calculations - for which values does a system of equations... » 2016-05-27 20:31:07
A 2 x 3?
#6 Re: Help Me ! » Matrix calculations - for which values does a system of equations... » 2016-05-27 20:17:46
I did. Yes. And I figured it might be a hint to the solution maybe not existing with the different shape?
#7 Help Me ! » Matrix calculations - for which values does a system of equations... » 2016-05-27 02:38:43
- NadineSch
- Replies: 13
Hello there. I find myself stuck with a matrix exercise:
Consider the matrices
A= ( k 3 0
8 2 -1
0 k 1)
and
B= (1 4 2
2 0 -2)
k is a parameter, element of IR
b) For which value(s) of k, if any, does the matrix equation AM=A+M have a unique solution for M?
c) let k=5. Find all solutions M, if any, of the matrix equation AM=B, respectively MA=B
For a I already found a solution so I won't bother you with it.
For these two others I am lacking an idea how to even start this and google doesn't help because it is to specific I guess.
So, any advice, hint, idea and ideally showing of steps will be greatly appreciated.
Thank you,
Nadine
#8 Re: Help Me ! » Maths Exam and no clue » 2016-05-27 00:41:51
I think I've got it, sorry, I was desperately trying to expand the quadratic to have the solution jump at me, but it worked by taking the discriminant 
#9 Help Me ! » Word problem differential equation » 2016-05-16 05:34:04
- NadineSch
- Replies: 4
Hello dear Mathlovers (I wish I can soon say I'm one of you ;-))
I have an exam upcoming and part of it is about differential equations. We got some exercises to study with along with solutions. But: It's only the actual solution, so not showing how to get there. I have one exercise in particular that I struggled with, because I made calculations and they seem to make perfect sense. But as I compared it to the solutions at the end: Not the same 
So I was hoping that you could help me out here. Especially with the calculations so that I can follow/compare/see where I went wrong etc.
Here it is:
On normal weekdays on average 18 customers per minute want to pay at the cash desk in a supermarket. At a cash desk it takes on average 2 minutes to serve a customer. To avoid long waiting times, one cash desk is opened per 10 customers in the queue.
a) Construct a differential equation that models the evolution of the number of customers queuing for the cash points in time.
b) Derive a function that describes the number of queuers for the cash desks in the supermarket at each time of the day. When the supermarket opens in the morning, there are no customers waiting at the cash desks, of course.
c) What is the maximal number of cash desks that simultaneously will be operational in the course of the day ?
d) In the long run, what will be the (average) waiting time for a customer at the cash desks ?
Thank you so very much indeed.
Nadine
#10 Re: Help Me ! » Maths Exam and no clue » 2016-05-16 05:23:56
Thank you very much! That was very helpful indeed. I had 0 as a solution for the first one, but I simply could not make sense of it...
bobbym (or anyone else), could you write out how you got the determinant and with that found the solution? I end up with -k^2+2k-24 and don't see how I can expand that to have the answer visual
#11 Re: Help Me ! » Maths Exam and no clue » 2016-04-25 20:58:37
Hi bobbym. Thank you! IR was my attempt to write out the sign for real numbers
Is there any way you could get the way to your answers to me? As that is where I struggle. I find exercises with solutions but it doesn't help me because I am insecure about the steps to reach it...
#12 Re: Help Me ! » Maths Exam and no clue » 2016-04-25 04:30:38
Thank you! Here they come
1. Compute (by hand) the area of the planar region enclosed by the graph of the function
f(x)= (6x-18)/(6x-x^2-5), the x-axis and the vertical lines x=2 and x=4
2. General solution (in implicit form) of the differential equation (1-y^3) y' - x^3 (lnx)^2 sqrt(4y-y^4) = 0
3. Consider the matrices
A= ( k 3 0
8 2 -1
0 k 1)
and
B= (1 4 2
2 0 -2)
k is a parameter, element of IR
a) For which value(s) of k, if any, is A an invertible matrix?
b) For which value(s) of k, if any, does the matrix equation AM=A+M have a unique solution for M?
c) let k=5. Find all solutions M, if any, of the matrix equation AM=B, respectively MA=B
#13 Help Me ! » Maths Exam and no clue » 2016-04-24 23:25:09
- NadineSch
- Replies: 12
Dear maths geeks (and I mean that as a compliment!!!)
I am in the middle of the preparation of my maths exam which is the final chance to succeed my studies. Whilst I successfully solve many exercise questions, there is a list of exercises that I know will be part of the exam, that I just CANNOT get to grips to
The general topics are Integrals, Differentials and Matrix calculations.
Is there anywhere where I can find help, maybe submit the exercises and find someone that actually enjoys solving them and sharing with me how to get there?
Thank you so very much in advance for anything. Tips, advice, contacts?
A very desperate Nadine
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