2011-05-06, 01:25 PM
OB3LISK Wrote:*cricket cricket*
*waits for Rust or Corn*
I was thinking of Noah. Maybe Russt might know, but I think Corn is still studying single-variable calculus.
modular Wrote:it doesn't? (equations 7.5 / 7.6)
For (7.5), they have f''(a)(x-a)^2+f'(a)f'(b)(x-a)(y-b)+f''(b)(y-b)^2. There should be a coefficient of 2 in the middle term. They do something similar for (7.6). I'm not sure why they left the coefficients out.
Noah Wrote:
Hmm... doesn't that run into the same problem as mine? That gives me an idea though:
![[Image: equationv.gif]](http://img24.imageshack.us/img24/5409/equationv.gif)
How would I express this for variables? In the notation I used in the first post, I can just add a (z-z0)(d/dz) term inside the brackets without losing anything, but I don't think I can do the same thing here. For example, if I did use this notation, if a=x-x0, b=y-y0, and c=z-z0, I would lose the 6abc term the expansion of (a+b+c)^3. Or am I supposed to lose that term?

![[Image: 6gxqxtd.png]](http://mathurl.com/6gxqxtd.png)