B1)m=-3y=-6x^2+4x+2=-6(x-1/3)^2+8/3 顶点(1/3,8/3)2)y=2mx^2+(1-m)x-(1+m)=0 x1+x2=(m-1)/2m x1x2=-(m+1)/2m |x1-x2|=√(〖( (m-1)/2m)〗^2+(4(m+1))/2m) =(3m+1)/2m=3/2+1/(2m)>3/24)m=0时 y=x-1 过同一点