— He has a sore back.
A:What is he
B:What does he do
C:What's the matter with him
D:What does he look like
已知:二次函数y=ax2+bx+6(a≠0)的图象与x轴交于A,B两点(点A在点B的左侧,与y轴交于点C,点A、点B的横坐标是一元二次方程x2﹣4x﹣12=0的两个根.
车轮要做成圆形,实际上就是根据圆的特征( )
下列最适合种子萌发的环境是