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## #1 Re: Help Me ! » Product of elementary matrices » 2012-10-17 08:29:03

Yes that was also the next question in the exam paper I did, worked out perfectly at the end

## #2 Re: Help Me ! » Product of elementary matrices » 2012-10-16 23:04:47

Hi Bob thanks a lot for all the effort.  I had no idea how to multiply more than 2 matrices so I tried doing all 3 at once...

## #3 Re: Help Me ! » Product of elementary matrices » 2012-10-16 04:17:36

Hi Bobbym any idea where I made a mistake?
Thanks a lot

## #4 Help Me ! » Product of elementary matrices » 2012-10-16 01:17:54

Deon588
Replies: 12

Hi all.  I think i'm making a mistake somewhere as the matrix I get after multiplying doesn't seem to be invertible and the next question is to find A^-1.  Is this the right way to do this?

## #5 Re: Help Me ! » Principal argument of the polar form of a complex number » 2012-10-11 19:54:59

Thanks Bob your explanation once again makes me able to move forward!!!

## #6 Help Me ! » Principal argument of the polar form of a complex number » 2012-10-10 21:06:41

Deon588
Replies: 3

Hi all i'm not sure at all how to proceed with this problem, I need to find the principal argument of z but not sure how to go about it...  After googleing I found (theta +2k(pi) =x/r so if I understood correctly (theta +2k(pi) =1/2?

## #7 Re: Help Me ! » Linear algebra: intersection » 2012-10-07 23:09:04

Hi Bob
I made a big mistake, I have a newer edition of the prescribed book which has a chapter on eigen values added.  I just checked on my study guide and see it's only the basic complex number theory that I need to study
Thanks for taking a look at it anyhow
Deon

## #8 Re: Help Me ! » Linear algebra: intersection » 2012-10-06 21:28:16

Hi Bob
Yes of course I attached 3 questions
Thanks

## #9 Re: Help Me ! » Linear algebra: intersection » 2012-10-06 05:57:28

Thanks again that totally clears it up for me.
I have another question for you:)  I recently lost a month of studying because of medical issues...  The only part of Linear algebra I haven't covered is the chapter dealing with eiggen values (not sure if I spelled that correctly) I see that some complex number skills are required for that chapter and i've never done complex numbers before.  I went through the past 3 years exam papers of my university and it seems like eigen vallues rarely appears and if it does it counts maybe 7/100 marks.  i'm writing Linear algebra on 23/10 so not much time left.  So right now i'm not sure at all whether just to forget about the eigen values and focus on the other work or try to learn some basic complex number theory and do the eigen value chapter as I have 4 other subjects this semester...  What would you recommend I do?  would it be possible to learn enough about complex numbers to use in a elementary linear algebra course?
Thanks

## #10 Re: Help Me ! » Linear algebra: intersection » 2012-10-06 03:24:09

the emoticon is supposed to be =

## #11 Re: Help Me ! » Linear algebra: intersection » 2012-10-06 03:23:08

Hi Bob!!!
Good to know you're still on these forums, I remember you helped me get past a lot of challenging problems last year.
I think so, is this the way to do this?  Sorry for the bad notation i'll have to go over the LaTeX post again...
x=p+t(q-p)
(x,y,z)=(2,4,-1)+t((5,0,7)-(2,4,-1))
(x,y,z)=(2,4,-1)+t(3,-4,8)
x=2+3t
y=4-4t
(x,y)=(2+3t,4-4t)
Thanks a lot

## #12 Help Me ! » Linear algebra: intersection » 2012-10-05 03:03:16

Deon588
Replies: 10

Hi all I recently started linear algebra and my prescribed book seems to require some 3-dimensional geometry knowledge which i've never touched...  Any idea how to go about this?
Let L be the line that passes through the points P(2,4,-1) and Q(5,0,7) Determine the point of intersection of L and the x-y plane
Should the z-coordinate be 0 because the question only mentions the x-y plane?
Thanks

## #13 Re: Help Me ! » Exponential equation » 2012-01-03 04:31:27

Hi Bobbym I think that's a bit above my level at this stage...

## #14 Re: Help Me ! » Exponential equation » 2012-01-03 04:27:54

Hi Anonimnysteffy Thanks a lot I understand what happens now.
Can you please show me what you mean by I should group stuff?
Should I break it up like

## #15 Help Me ! » Exponential equation » 2012-01-03 02:05:03

Deon588
Replies: 7

Hi all I have no idea how to start this equation the exponential equations I have done so far were all more or less the same (becomming a quadratic equation which made it very easy to solve X)

How do I start this?  should I somehow devide everything by 3?

## #16 Re: Help Me ! » Applications of Logarithms problem » 2011-10-20 01:38:01

Hi Bob.  I'm not allowed to use a calculator in my exam so I probably don't have to do this?
Thanks a lot.

## #17 Help Me ! » Applications of Logarithms problem » 2011-10-19 19:07:16

Deon588
Replies: 2

Hi all.  Does this look ok?  I didn't pay much attention to this work during the year and writing maths tomorrow...  Is there a way to simplify this further?  and would it be ok to leave it as a logarithm and just write grams afterwards?

## #18 Re: Help Me ! » Word problem equation problem » 2011-10-17 01:56:39

We also write coordinates on the cartetian plane as (x;y) and not (x,y)

## #19 Re: Help Me ! » Word problem equation problem » 2011-10-17 01:53:58

Hi.  I just came back to this post to check my method for a simular problem and noticed the new posts.  Consideryouranswer in South Africa we use a , to represent a decimal so the way Bob did it works perfectly for me.  Here 3.4 is always 3*4 and 3,4 is the decimal

## #20 Re: Help Me ! » Word problem » 2011-10-11 10:50:58

Bob thanks a lot for that very detailed explanation, as usual u completely cleared it up for me:).

## #21 Re: Help Me ! » Word problem » 2011-10-11 00:05:24

Hi Bob.  That's the part which confuses me.  isn't

Thanks a lot for checking

## #22 Re: Help Me ! » Word problem » 2011-10-10 22:05:59

So it will take Machine B 4 hours to fill the bottles?

## #23 Re: Help Me ! » Word problem » 2011-10-10 21:54:36

Thanks a lot Bobbym.  so

## #24 Re: Help Me ! » Word problem » 2011-10-10 20:50:29

I see some of the LaTeX lines are very close to each other.  Is there a way to avoid this?  Or should I just leave a line open?