Let f(.) be a twice differentiable function from \(\R^2\rightarrow\R\). If p, x0 ∈ \(\R^2\) where ||p|| is sufficiently small (here ||. || is the Euclidean norm or distance function), then \(f(x_0 + p) =f(x_0) + \triangledown f(x_0)^Tp+\frac{1}{2}p^T\triangledown^2f(\psi)p\) where \(\psi\isin\R^2\) is a point on the line segment joining x0 and x0 + p. If x0 is a strict local minimum of f(x), then which one of the following statements is TRUE?