如图，质量分别为2m和m的A、B两物体通过轻质细线绕过光滑滑轮.弹簧下端与地面相连，上端与B连接， A放在斜面上，斜面光滑.开始时用手控住A，使细线刚好拉直，但无拉力，此时弹簧弹性势能为E_P.滑轮左侧细线竖直，右侧细线与斜面平行.释放A后它沿斜面下滑，当弹簧刚好恢复原长时，B获得最大速度.重力加速度为g，求：

方程（x+1）（x-2）=1的根是____。

    My name is Dave. I have three good friends, Jack, Tom and Jim. Jack likes cakes, Tom likes fruit, Jim likes eggs and I like vegetables. We all like hamburgers. We eat hamburgers for lunch every day. Jack and Tom like French fries , and I also(也) like French fries, but Jim doesn't like them. For dinner, I don't like chicken,    ⑶    Jack, Tom and Jim like it. They all think chicken is very delicious.

根据短文内容，回答下列问题。

在一个以屈肘肌肉为效应器的反射弧中，如果传出神经受到损伤，而其他部分正常，当感受器受到刺激时将表现为（　　）

豌豆果皮绿色（D）对黄色（d）为显性，若将绿色豌豆（Dd）的花粉授到黄色豌豆（dd）的柱头上，则黄色豌豆上所结果实的颜色和种子中胚的基因组成分别是（　　）