Question

10.若集合A={x|x2+x-6=0} B={x|mx+1=0}且B A,则实数m的取值个数是（）.

Answer 1

x2+x-6=0 x=2或-3 A={2,-3} 当m=0,B为空集,满足B A ２m+1=0,m=-1/2 -3m+1=0,m=1/3 有３个