The relationship between y and x is described as partly constant and partly varies inversely as the square of x. This can be expressed as:

y = constant + \(\frac{constant}{x^2}\)

Now, let's look at the answer choices:

A. y = Q + \(\frac{P}{x^2}\) - This matches the given relationship, so it's a possible answer.

B. y = Q + px - This doesn't include the inverse square relationship, so it's not a correct choice.

C. y = \(\frac{PQ}{x^2}\) - This includes the inverse square relationship but doesn't have a constant term, so it's not a correct choice.

D. y = Q - \(\frac{P}{x^2}\) - This includes the inverse square relationship but has a minus sign instead of a plus sign for the constant term, so it's not a correct choice.

Based on the description of the relationship as partly constant and partly varying inversely with the square of x, the correct answer is y = Q + \(\frac{P}{x^2}\).