(1,-4)则y=a(x-1)²-4过(0,-3)-3=a-4a=1所以y=x²-2x-3x轴则y=0(x-3)(x+1)=0x=3,x=-1所以AB=|3-(-1)|=4即三角形底边是4高是C到x轴距离是4所以面积是8
