Homework Statement
Suppose F: Rn --> R has first order partial derivatives and that x in Rn is a local minimizer of F, that is, there exists an r>0 such that
f(x+h) \geq f(x) if dist(x, x+h) < r. Prove that
\nabla f(x)=0.
Homework Equations
We want to show that fxi(x) =0 for i = 1,...,n
So...