A: 过滤
B: 点燃酒精灯
C: 检查装置气密性
D: 稀释浓硫酸
已知M、N两点关于y轴对称,且点M在双曲线y=12x上,点N在直线y=x+3上,设点M的坐标为(a,b),则二次函数y=﹣abx2+(a+b)x( )
- He is never late for school.
- ______. His teacher is angry with him.
作简谐运动的物体每次通过平衡位置时( )