Prove
- that the sum of multiplicities of two singular points of an irreducible curve of degree $n$ is at most $n$,
- sum of multiplicities of any 5 points is at most $2n$.
I tried to use Bezuot theorem.
Let $P$ and $Q$ are points with multiplicities $p<n$ and $q<n$, then the line $L$ intersects the curve $C$ at least at $p+q < 2n$. As the curve C is irreducible, this number is $n$.
I guess The Bezuot theorem is useful here but I have no idea how to applay it.
Could someone check the first proof and correct it if it's wrong and give me idea how to prove the second?