2x^2-4mx+(2m^2-4m-3)=0
y=x1^2+x2^2
=(x1+x2)^2-2x1x2
=4m^2-(2m^2-4m-3)
=2m^2+4m+3
m的取值就是判别式>=0
即16m^2-8(2m^2-4m-3)>=0
==>2m^2-2m^2+4m+3>=0
==>m>=-3/4
2x^2-4mx+(2m^2-4m-3)=0
y=x1^2+x2^2
=(x1+x2)^2-2x1x2
=4m^2-(2m^2-4m-3)
=2m^2+4m+3
m的取值就是判别式>=0
即16m^2-8(2m^2-4m-3)>=0
==>2m^2-2m^2+4m+3>=0
==>m>=-3/4