(1)设y=a(x^2-4x-12),它过点(0,-4),
∴-4=-12a,a=1/3,
∴抛物线的解析式为y=(1/3)(x^2-4x-12).
(2)A(-2,0),B(6,0),
BC:y=(2/3)x-4,AC:y=-2x-4.
设M(m,0),-2
(1)设y=a(x^2-4x-12),它过点(0,-4),
∴-4=-12a,a=1/3,
∴抛物线的解析式为y=(1/3)(x^2-4x-12).
(2)A(-2,0),B(6,0),
BC:y=(2/3)x-4,AC:y=-2x-4.
设M(m,0),-2