Question

设集合A={x丨丨x-a丨<1，x∈R}，B={x丨1<x<5,x∈R，}若A∩B=∅，则实数a的取值范围是

Answer 1

a-1<x <a+1
a+1<=1 a-1>=5
所以a<=0 a>=6

Answer 2

A = { x| -1+a <x<1+a }
B={x|1<x<5, x∈R}
A∩B=∅
1+a<1 or -1+a >5
a<0 or a>6