(4x+2n)/(x+m)=x(x+m)/(x+m)
(xx+mx－4x－2n)/(x+m)=0
(xx+mx－4x－2n)=0
xx+(m－4)x－2n=0
有两个绝对值相等,符号相反的根
xx+(m－4)(-x)－2n=0
m－4=0
m=4
(xx－2n)/(x－4)=0
m=4
n>0即可