Which of these equations has infinitely many integer solutions?
x2+y2=1x^2 + y^2 = 1x2+y2=1
x+y=5x + y = 5x+y=5
x2−y2=1x^2 - y^2 = 1x2−y2=1
x2+y2=0x^2 + y^2 = 0x2+y2=0