A:动滑轮的重力
B:被提升物体的重力
C:承担物重的绳子股数
D:物体被提升的高度
----You park here! Look at the sign, it says “No parking”.
----Sorry, I didn't notice that sign just now.
已知n正整数,且x2n=2,求(3x3n)2﹣4(x2)2n的值.
如图,若a∥b,∠1=60°,则∠2的度数为( )