For the Bernoulli equation y′+y=y3y' + y = y^3y′+y=y3, which substitution is correct?
v=y2v = y^2v=y2
v=y−2v = y^{-2}v=y−2
v=y−3v = y^{-3}v=y−3
v=y3v = y^3v=y3