正方形有____条对称轴,长方形有____条对称轴,圆有____条对称轴。
已知a>0,x,y满足约束条件x≥1y≥a(x-3)x+y≤3若z=2x+y的最小值为1,则a=( )
支持宇宙大爆炸理论的科学发现是( )
--- Excuse me. Is there a pay phone near here?
--- No, . Maybe you can ask the police.