Question

设m=(x/x^2-3x+2=0),n=(x/mx+2=0)若mn=n求实数m的值所组成的集合

Answer 1

M={x|x^2-3x+2=0 }

= { x| (x-1)(x-2)=0 }

={ 1,2 }

N = {x| mx+2=0 }

= { x | x= -2/m }

if M∪N = N => M is subset of N

x= 1 ,=> m = -2

x= 2,=> m = -1

m的值所组成的集合

={ -2,-1}