Affine-scaling symmetry of u double prime equals u prime squared over u minus u squared
= Affine-scaling symmetry of u double prime equals u prime squared over u minus u squared
{title2=$u''=(u')^2/u-u^2$}
The vector fields $(cx+d)\partial_x-2cu\partial_u$ generate
$$
(x,u)\longmapsto(\lambda x+a,\lambda^{-2}u).
$$
Their second prolongations multiply the differential equation by $-4c$, so they are infinitesimal Lie symmetries.