A:walked;noticed
B:walked; had noticed
C:walks; has noticed
D:had walked; noticed
______swimming here. It's dangerous.
课____ 想____ 怪____
棵____ 相____ 圣____
函数f(x)的定义域D={x|x≠0},且满足对于任意x1,x2∈D,有f(x1•x2)=f(x1)+f(x2).
(1)求f(1)与f(﹣1)的值;
(2)判断函数的奇偶性并证明.
下列关于动物类群的主要特征正确的是( )
已知抛物线与x轴交于A(6,0)、B(﹣ 54 ,0)两点,与y轴交于点C,过抛物线上点M(1,3)作MN⊥x轴于点N,连接OM.