Section Aux.
Definition andb_assoc := Bool.andb_assoc.
Variable R : realFieldType.
Variable n : nat.
Definition Vector := 'rV[R]_(n.+1).
Implicit Types (v : Vector).

Lemma bet_neq0 (k1 k2 k3 : R) :
0 < k1 -> 0 < k2 -> k1 < 1 -> 0 < k3 -> (k1+k2-k1*k2)/k3 != 0.