GMAT Problem Solving (PS) | Re: If the expression x^2 – xy/5 + 25 can be expressed by (x – 5)^2, what

Here y can take any value if x equals 0 and the question does not state that x is not equal to 0. In that consideration, shouldn't the answer be "Cannot be determined"? I think the answer should be D (i.e.: y=50) only if the question explicitly mentions that x does not equal 0.