Question

Hey guys , i am currently in lecture 10. I totally understand where the linear approximation comes from. But i don;t quite get how we derived the quadratic approximation. Has the professor explained it already or did he just state it with a plan of explaining where it comes from later. I assume it has something to do with Taylor expansion?

Answer 1

There's a good explanation in the end of lecture 9 when he does a quadratic approximation of a quadratic equation, and proves (as expected) that the best quadratic approximation of a quadratic equation is itself.

Using the lecture clips from the Scholar 2010 course is sometimes confusing - I'm following the lectures from the 2006 and checking with the 2010 website.

Answer 2

Yes, you are right. You can see the quadratic approximation as Taylor expansion but without terms whoose order higher than 2.