R为全集,A={x|x-3>=4},B={x|5/(x+2)>=1},则(CRA)交B=?
问题描述:
R为全集,A={x|x-3>=4},B={x|5/(x+2)>=1},则(CRA)交B=?
答
A={x|x-3>=4}={x|x>=7},
5/(x+2)>=1
5/(x+2)-1>=0
[5-(x+2)]/(x+2)>=0
(-x+3)/(x+2)>=0
即(x-3)/(x+2)得-2