Please prove or disprove that, for symmetric matrix $A=A^T$, we have
$$\max_{x \in \{\pm 1\}^n} x^T A x \geq \mbox{Tr}(A)$$
Please prove or disprove that, for symmetric matrix $A=A^T$, we have
$$\max_{x \in \{\pm 1\}^n} x^T A x \geq \mbox{Tr}(A)$$