Question

已知A={x|x2+x-2=0},B={x|mx+1=0},且A∪B=A,求实数m的取值范围.

Answer 1

A={x|x2+x-2=0}

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

= {-2,1}

A∪B=A

=> B is subset of A

when x =-2

mx +1 =0

-2m +1 =0

m = 1/2

when x =1

mx +1 =0

m +1 =0

m = -1

ie m= -1 or 1/2