What is the answer to this problem?

SAT_Questions
Tue, 03 Jun 2008 00:21:25 +0000

If (x + y)2 = x2 + y2, which of the following statements must also be true?

x = 0
(x - y)2 = x2 + y2
xy = 0
None

I only

II only

III only

II and III

iii only right? (all the 2’s are squares)