序号

形状

${\alpha }_1$

${\alpha }_2$

${\alpha }_3$

1

倒U形

${\alpha }_1>0$

${\alpha }_2<0$

${\alpha }_3=0$

2

单调递增

${\alpha }_1>0$

${\alpha }_2=0$

${\alpha }_3=0$