(1)交点式代入y=a(x-3)(x+1),过点C(0,-3)带进去求出a就好了
y=(x-3)(x+1)
(2)op连线,设点p为(x,y)
s四边形AOCP=S△ocp+s△opA=1/2×3×X+1/2×3×(-y)=3/2(X-y)
(x-y)=x-(x-3)(x+1)=x-(x^2-2x-3)=-x^2+3x+3
X=3/2Y=21/4S四边形AOCP=3/2×21/4=63/8
p点y=(3/2-3)(3/2+1)=-15/4
p点(3/2,-15/4)如果是求四边形ABCP的最大面积为75/8,p点也是这个(3/2,-15/4)