Which of the following Pell-like equations has no integer solution (x,y)(x, y)(x,y)?
x2−2y2=1x^2 - 2y^2 = 1x2−2y2=1
x2−3y2=1x^2 - 3y^2 = 1x2−3y2=1
x2−4y2=2x^2 - 4y^2 = 2x2−4y2=2
x2−5y2=1x^2 - 5y^2 = 1x2−5y2=1