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. Well, then we could solve, we can figure out what y is in terms of x, and then substitute. So let's do that right over here. If we divide both sides by x, we get y is equal to negative 16 over x.