So I'll just call that the sum of the squares, s for sum of the squares, and it would just be equal to x squared plus y squared. And this is what we wanna minimize. We want to minimize, minimize s. Now, right now, s is expressed as a function of x and y. We don't know how to minimize with respect to two variables, so we have to get this in terms of only one variable, and lucky for us, they give us another piece of information. Their product is negative 16. So x times y is equal to negative 16. So let's say we wanted this expression right over here only in terms of x.