# Economists Do It With Models

## Lagrange Multipliers, Or Econgirl’s Foray Into Real Math…

#### January 30th, 2012 · 6 CommentsFun With Math · Videos

I get very frustrated when people say things like “I can’t do economics because I’m not good at math,” since I feel strongly that basic economics isn’t about math, and there is plenty that people can understand about economics without trudging through a bunch of algebra.

That said, I am teaching graduate students this semester, and it’s pretty much impossible to avoid the math in that context, for better or for worse. Personally, I like math, so getting to work through more advanced stuff is fun for me, but it’s a challenge because it’s really hard to tell what my students have and haven’t learned (or remember or don’t remember). Which brings us to Lagrange multiplier videos…

The Lagrange multiplier is a mathematical technique for solving constrained optimization problems, such as maximizing utility subject to a budget constraint or minimizing cost subject to a quantity constraint. I had to use it to derive a particular formula in my macro theory class, and I realized afterwards that it left some of my students more than a little befuddled, so I made some videos as a review/tutorial. The funny part is that I really had to think about why the technique works, since in the past I’d mostly just taken it for granted in my quest to finish my problem sets as quickly as possible.

*I* think that the concept of Lagrange multipliers is interesting regardless of whether you have an immediate need to use them, but I will leave you to judge for yourselves:

You can see both the videos and articles organized in what I hope are useful ways here. You may have also noticed that the latest articles are posted in the left sidebar under “Econgirl at About.com” and the latest videos are posted in the right sidebar under “Economics Classroom.”

Tags: Fun With Math · Videos

### 6 responses so far ↓

• 1 Punditus Maximus // Feb 1, 2012 at 11:16 am

Yeah, LaGrange stuff was fun to learn, though of course behavioral econ has made clear that absolutely nobody thinks in these terms.

• 2 Robert // Feb 1, 2012 at 9:55 pm

Funny. I just assumed the site was written by a male till I saw these videos. Sorry.

• 3 Punditus Maximus // Feb 3, 2012 at 4:11 am

@Robert: what did you think all the pictures of the same woman holding economics texts along the side were? I think you may have learned something important, sadly.

• 4 Robert // Feb 3, 2012 at 8:10 pm

You know, I was more focused on the text, and what you had to say than the photos. I suppose that should be a compliment, although the photos are awesome now that I’m paying attention.

I don’t remember what link it was that brought me here originally, it was probably Ace or Powerline, but I liked it so much I bookmarked your site. However, its been a long time since I checked back. I don’t remember photos on the sidebar last time I was here.

• 5 Punditus Maximus // Feb 5, 2012 at 7:16 pm

Fair ’nuff, just saying. These days, there’s no such thing as “default” gender, ya know?

• 6 asian sensation // Jan 23, 2013 at 4:09 pm

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