#[deprecated(since="8.16",note="Use Rsqr_inv'.")]
Notation Rsqr_inv := Rsqr_inv_depr.

Lemma canonical_Rsqr : forall (a:nonzeroreal) (b c x:R), a * Rsqr x + b * x + c = a * Rsqr (x + b / (2 * a)) + (4 * a * c - Rsqr b) / (4 * a).