[Milan.]

simple question, but im just stuck with one small thing on part iii) how did the answers get (4,-6,-1) i got the 4 and -6 from the partial derivatives of f
but where does the -1 come from??

thanks for any help

[Milan.]

heeelppp

[ghostwalker]

Couple of methods:

Either, see about a third of the way down on http://tutorial.math.lamar.edu/Class...gentPlane.aspx, where he introduces z=f(x,y).

Or, Consider fx and fy as two vectors and form their cross product, to get a normal vector.

This latter method may be none standard, as I can't recall any multivariate calculus.