初中二次函数题二次函数y=ax^2+bx+c中,设a=2m,b=1-m,c=-1-m.下面的四个结论1、当m=-3时,函

选B.
y=ax^2+bx+c=2mx^2+(1-m)x-1-m
1, 正确：y=-6x^2+4x+2=-6(x-1/3)^2+8/3
2,正确：2mx^2+(1-m)x-1-m=0
x1=-(m+1)/(2m),x2=1
|x2-x1|=|1+(m+1)/(2m)|
=|3/2+1/(2m)|
∵m>0
∴3/2+1/(2m)>3/2
|x2-x1|>3/2
3, 错误：y=2mx^2+(1-m)x-1-m
=2m[x+(1-m)/(4m)]^2-(9m^2+6m+1)/(8m)
对称轴为x=(m-1)/(4m)=1/4-1/(4m)
∵m>0
∴1/4-1/(4m)>1/4
4,正确：由第二部分可知,当y=0时,x=1
因此函数图像经过同一点(1,0)