Question

如图,在平面直角坐标系中,直线y=-3x-3与x轴交与点A,与Y轴交与点C,抛物线y=x^2+bx+c经过A C两点,且

Answer 1

y=-3x-3

y=0,x=-1,A(-1,0)

X=0,Y=-3,C(0,-3)

c=-3

0=1-b-3,b=-2

Y=X^2-2X-3=(X-3)(X+1)=（x-1)^2-4

B(3,0)

3-1=2,2/2=1

X=1为抛物线的对称轴,顶点D(1,-4)

2、

F(m,n)

BC:Y=X-3,M(m,m-3)

Ye=m^2-2m-3;E(m,m^2-2m-3)

ME=m-3-m^2+2m+3=-m^2+3m=-(m-3/2)^2+9/4

MEmax=9/4

3、

M(3/2,-3/2)