题目

Owls(猫头鹰) are mysterious creatures. We often think of them as scary. They sometimes live in abandoned houses. They fly without a sound through backyards at night. In stories, they appear with ghosts. When we hear an owl's familiar “wh­ooo...whooo...”，it can make us feel very frightened. Owls fly silently, without even a whisper of wings moving through the air. It's as though they appear out of nowhere—like ghosts on wings. Owls fly and hunt on the darkest of nights. An owl's night habits make it unique. Do these creatures of the night possess strange powers? Owls possess 已知A={x|1≤x≤2}，B={x|x2+2x+a≥0}，A、B的交集不是空集，则实数a的取值范围是a≥-8a≥-8．