键一般分()、()和钩头键三种。
参考答案:普通平键;半圆键
已知抛物线C:y2=2px (p>0)上一点P(6,m)到其焦点F的距离为7,则抛物线C的以点M(2,1)为中点的弦AB所在直线的方程为______.
I think the Internet is very helpful. --()
A.Yes, so do I .
B.That’s a very good idea
C.Neither do I
D.I’d rather go surfing on it