过抛物线C:y=x^2上两点M,N的直线L交Y轴于点D{0,b} 1,若角为钝角{O为坐标原点},求实数B的取值范围

理念是设线,求点,MN²>MO²+NO²
设直线为y=kx+b
kx+b=x² x²-kx-b=o
M(p,p²),N(q,q²) p+q=k pq=-b
MN²=(q-p)²+(q²-p²)²
MO²=p²+p^4
NO²=q²+q^4
-2pq-2p²q²>0
p²q²+pq