有足球72个,正好是篮球个数的8倍,篮球有多少个?
72÷8=9(个),
答:篮球有9个.
过圆x2+y2=4外一点P(2,1)引圆的切线,则切线的方程为______.
一It's said that aliens tried to warn the astronauts on the moon to _____.
一Maybe they didn't like human beings to get close to them.[ ]
A.stay up
B.stay out
C. stay away
D.stay behind