分解因式：x4﹣x2y2=____ ．
设m∈R,命题“若m>0,则方程x2+x-m=0有实根”的逆否命题是( )
家是我们：（ ）①情感的栖息地 ②物质生活的后盾 ③发泄不满的地方 ④发展的大本营
As students, you must listen to the teacher attentively and keep a record ______ what the teacher says in class.
