(1)x^2+mx-2m^2 = 0
delt = m^2 + 8m^ = 10m^2 >0
(2)m0
y=n时,x^2+mx-2m^2 = n, (x+m/2)^2 = n+(9m^2)/4 > 0,即n>-(9m^2)/4
假设x1m/2时,n + 2m^2>0, n>-2m^2
2PB = 2|x2| =-m + √[n+(9m^2)] = AP = m/2 + √[n+(9m^2)/4]
3m = √[n+(9m^2)], n=0,满足不等式条件,此时要求m>0,两交点分别在y轴两侧
当 √[n+(9m^2)/4]