已知集合A=[x|x^2=1｝,B=｛x|ax=1｝.若B是A的子集,求实数a的值

题目

已知集合A=[x|x^2=1｝,B=｛x|ax=1｝.若B是A的子集,求实数a的值

答案

A=[x|x^2=1｝
= { -1,1}
B is subset of A
then
ax =1
a = 1/x ( x = -1 or 1 )
= -1 or 1 #