Let $k$ be a field. How to show that $k[t]$ is not flat as a module over $k[t^2,t^3]$ ?
Since the ring extension $k[t^2,t^3]\subseteq k[t]$ is integral, it is clear that $k[t]$ is a finitely generated $k[t^2,t^3]$-module , and also torsion free. I am unable to proceed further.
Please help. Thanks in advance.