若关于x的方程x²+2x+a=0不存在实数根，则a的取值范围是（　　）

分解因式 mn -8=____． 

阅读下面的短文，根据短文内容及首字母提示，在短文空白处填入一个恰当的词，使短文内容完整、通顺。

    Jimmy is a middle school student. He adopted（收养）three h____baby dogs two months ago. He took good c____of them and the dogs became healthier and fatter. Jimmy loved them very much. But now he feels w____.He has some problems. First, he has r____out of his money to buy food for dogs. Second, the dogs are too big and there is not e____room for them. Third, the dogs have become too noisy. So his mother hates them. She can't stand them.

    Some of Jimmy's friends are trying to c____ him up. Some advise（建议）Jimmy should p____up dogs' photos in the street and l____for their owners. Some suggest him calling the TV station f____help. Do you have any good i____to help him?

已知椭圆$E:\frac{x^2}{a^2}+\frac{y^2}{b^2}=1$（a＞b＞0）过点（0，$\sqrt{2}$），且离心率为$\frac{\sqrt{2}}{2}$。

(Ⅰ)求椭圆E的方程；

（II）设直线x    my    1,(m   R)交椭圆E与A,B两点，判断点G（-$\frac{9}{4}$,0）与以线段AB为直径的圆的位置关系，并说明理由。