Help Please

[Quanamay03]

If anyone knows how to do any of these..... help!!


Find the local max, and min and saddle values.

1. f(x,y)= x^2-xy+y^2+9x-6y+10

Find the directional derivative of F at the given point in the indicated direction.

2. f(x,y,z)=x^2y+x(sqrt(1+z)), (1,2,3), in the direction of v=2i+j-2k

 

[pka]

Here is some help with #2.
Given \(\displaystyle f(x,y,z) = x^2 y + x\sqrt {1 + z}\) then \(\displaystyle \nabla f(x,y,z) = \left( {2xy + \sqrt {1 + z} } \right)i + x^2 j + \left( {\frac{x}{{2\sqrt {1 + z} }}} \right)k\).

Now find the dot product \(\displaystyle \nabla f(1,2,3) \cdot \frac{v}{{\left\| v \right\|}}\)