I'm trying to minimize the following:
$P(x_{k+1}) = f(x_k) + \nabla f (x_k) \cdot (-h_k \nabla f(x_k)) + \frac{1}{2}(-h_k \nabla f(x_k))^T Hf(x_k) (-h_k \nabla f(x_k))$
I know that minimizing the quadratic form is by solving $Ax = b$ i.e. $x = A^{-1}b$, so how can I choose $h_k$ to minimize $P$.