A:You have a headache.
B:Maybe you have a fever.
C:You should see a dentist.
下面计算正确的是( )
of the children likes the movie because it's too boring.
广告费用x(万元)
3
4
5
6
销售额y(万元)
25
30
40
45
根据上表可得回归方程 y^ = b^ x+ a^ ,其中 b^ =7,则 a^ =____,据此模型预报广告费为7万元时销售额为____.
如图,是物体A通过凸透镜(透镜未标出)成像的示意图.当凸透镜放在哪点时,才能产生图中所成的像A′( )