集合A={1,2}共有____ 子集.
若x的值满足2x2+3x+7=8,则4x2+6x﹣9=____
No. 1 Middle School
Don't run in the hallways
Don't bring food into the classroom.
Don't listen to music in class.
You have to wear a uniform.
No. 2 Middle School
Don't bring food into the classroom
Don't wear a hat in class.
Don't go into the classroom without the teacher.
No. 3 Middle School
Don't listen to music in the classroom.
Don't run in the hallways.
You have to wear sports shoes for gym class.
某学习小组讨论辨析以下说法:①粗盐和酸雨都是混合物;②沼气和石油都是可再生能源;③冰和干冰既是纯净物又是化合物;④不锈钢和目前流通的硬币都是合金;⑤盐酸和食醋既是化合物又是酸;⑥纯碱和熟石灰都是碱.上述说法正确的是( )