— What are you going shopping for?
— I want to buy something for my son's birthday.
A:twelve
B:twelfth
C:the twelfth
D:the twelveth
若关于x的不等式组x+1>0x<a有解,则实数a的取值范围是____
一种变速自行车有3个前齿轮,6个后齿轮,一共能变化出9种不同的速度.
要得到y=3sin2x+π4的图象,只需将y=3sin2x的图象( ).