2 problems

Let $f:X\to\mathbb{P}^2$ be the blow-up of the projective plane in general points $P_1,\ldots,P_s$. A negative curve is a reduced and irreducible curve with negative self-intersect…

Let $f\colon X_r\to\mathbb P^2$ be the blow-up at $r$ very general points, with exceptional divisors $E_1,\ldots,E_r$, and write a divisor as $D=(d;m_1,\ldots,m_r)$, where…