# Maximum pointed devertive

1. Sep 13, 2004

### ori

the question
f(x,y,z)=Axy^2+Byz+Cx^3*z^2
given data: at point(1,2,-1) the maximum pointed devertive of f is
at direcation
x=0 y=0 z=1
and its value is 32
so what are they A,B ,C?

the only thing i know that since the func is differncial
and from here we get
B-C=16

but how do we get 2 more equation?
i dunno how to use the data that this is the max pointed devertive

2. Sep 13, 2004

### arildno

Remember that the gradient must be parallell to the direction of maximal "pointed" derivative!
$$\nabla{f}=(0,0,32)$$
Hence, you get 3 equations with 3 unknowns, one equation for each component.

3. Sep 13, 2004

### ori

thank u
how did u do the formula? (with the grad symbol)

4. Sep 13, 2004

### HallsofIvy

He used \nabla in a "tex" formula.

Click on any "tex" formula and you will see the code used.