Which of the following ODEs is NOT Bernoulli?
y′+y=xy3y' + y = xy^3y′+y=xy3
y′+xy=y−2y' + xy = y^{-2}y′+xy=y−2
y′+y=exy' + y = e^xy′+y=ex
y′+y2=xy' + y^2 = xy′+y2=x