Lagrange multipliers: Extreme values of a function subject to a constraint

[atreyukicks]

Wow Dr. Tisdell you are a remarkable prof! Even though I just came here for review after having learnt this already, I can tell all viewers that this is a spot on example/explanation of Lagrange multipliers! I wish you were a professor at Concordia University in Montreal, I would love to have you as a prof one day!

[sapmess]

Perfectly explained! I came here clueless after 2 hours in the textbook and left 7 minutes and 31 seconds later with full understanding

[swampwiz]

The hum in the background sounds like a UFO is ready to land.

[DrChrisTisdell]

@swampwiz Haha! Actually, it is the noise from the air-con units for the building that lie directly outside the window.

[ulivaldo]

Perfect!!! Thanks a lot

[DrChrisTisdell]

Great!! Thanks!

[PcKSnipE]

Is that how you pronounce Lagrange at 0:57 ? I said it that way and my tutor gave me the dirty haha :)

[DrChrisTisdell]

Hahaha!!! So much for my Aussie-French accent??!! :-)

[yoyaya007]

thanks . but how do u know that the two first points r maximun and the two others r minimum with out doing any seconde derivative.....?????

[DrChrisTisdell]

Hi Yoyaya. If you listen carefully, at 6.42 I discuss how to show which points lead to maxima and which points lead to minima.

In particular, if you evaluate $f$ at the first two points then you get $1/(2\sqrt{2})$. At the other two points $f$ has value $-1/(2\sqrt{2})$. It is easy to see that the maximum of these set of values is $1/(2\sqrt{2})$ and the minimum value is $-1/(2\sqrt{2})$. Thus, the 2nd-derivative test is not required.

Hope I am being clear here and thanks for watching!

[yoyaya007]

oh yeah !!! thank u

DrChrisTisdell it's very clear!

[Descott88]

Thanks for the explanation, I was stuck on the question and this cleared it all up.

[DrChrisTisdell]

Hey, happy to help!

[joycec122]

thanks so much chris!

i was stuck on this question for so long and now it seems so easy to do it now in the vid :)

i really like ur 2019 lectures :) :)

[DrChrisTisdell]

Thanks again Joyce!!

[fartx211]

i get all these Lagrange stuff now. I reckon Math2019 has been pretty good so far.

[DrChrisTisdell]

That's good to hear. Make sure you study the sample tests that I posted on My eLearning and best of luck with the class test.

[imadeanccountforthis]

very well explained gj and great videos

must take a long time to create :)

math2019

[DrChrisTisdell]

Thanks Imadean!

You're right. 5 minutes of video takes about 3-4 hours to film, produce and upload. That's why I try to keep it as simple as possible.

[moopoo666]

sweet as. this vid has helps heaps. it seems all good and well when you go through the examples in the 2019 lecture...that is, until I start doing tute problems. Thanks again!

[DrChrisTisdell]

I'm sure you' ll get the hang of the tute problems with a bit of effort and persistance. Also make sure you look at the sample class tests that I posted on My eLearning.

[SteveFlynn0]

Hey Chris,

Nice work mate, the vid is great for when I get stuck on the problem. Frees up tute time too, maybe in the future we can just skip the tutes and plug straight into youtube. Keep up the good work.

[DrChrisTisdell]

Hi Steve,

your suggestion was discussed with a few of the Profs here early this year. It might be an option int he future after a few more videos are posted. .....watch this space!

[nogigglingmajor]

I have always had to work very hard in maths, it is most definitely not my strong point. These help SO much, and you have a very good way of explaining problems. Thanks!

[DrChrisTisdell]

You're most welcome! : -)

By the way - keep working hard, keep thinking in simple terms and I know you'll do great with maths.

[CoreyR2009]

Extremely helpful... there's a good pun! Nice work, Please replace my professor at ASU!

[DrChrisTisdell]

Hey, "no worries" as us Aussies say. Happy to help!

[thaprofessor80]

Thanks for posting this. Very clear and easy to understand. Keep up the good work!

[DrChrisTisdell]

Thanks very much for your comments and rating. Your feedback is really important and I hope you find the site useful. More videos coming soon.

Chris