2x方-4x+m的跟为x1x2则 1/x1+1/x2＝
问题描述：
2x方-4x+m的跟为x1x2则 1/x1+1/x2＝
答
2x方-4x+m=0的跟为x1x2
∴x1+x2=2
x1x2=m/2
∴1/x1+1/x2
=(x1+x2)/x1x2
=2/(m/2)
=4/m