如图,已知二次函数y=ax2+ 32 x+c的图象与y轴交于点A(0,4),与x轴交于点B、C,点C坐标为(8,0),连接AB、AC.
Our English teacher is very kind ________us.
凸透镜的焦距是12cm,把点燃的蜡烛放在距凸透镜15cm处,则蜡烛通过凸透镜成()