I am looking forSuppose $A=k\oplus A_1 \oplus A_2\oplus \cdots$ is a quadratic algebra over a field $k$. Let $B$ be the subalgebra generated by a subspace $V\subseteq A_1$. What are the examples of such subalgebras of quadratic algebras$B$ that are not quadratic itself?
Became Hot Network Question
