Making a Quadratic Function spit out Integer Outputs for Rational Inputs
Suppose I have a quadratic function
and I want to find rational (non-integer) values of x for which .
Let . Let A be a positive-definite symmetric matrix. Is there a general formula for ?
For example, let
Then
This is equal to where is the Hadamard product of x,y.
It seems that also works for . Is this true in the general case, and if so, how do I prove it? If not, how can I find and prove a general formula?