读图,回答下列问题.
下列句子中都是名词的一组是( )
长妈妈曾经讲给我一个故事听:先前,有一个读书人住在古庙里,晚间,在院子里纳凉的时候,突然听到有人在叫他。
Learning English online
Ways to learn English
English magazines, newspapers and radio
Various kinds of English learning1.
Benefits of online learning
People around the world can visit them 2.
People can get answers instantly on the Internet.
People can learn what they need anytime and search for useful3 without leaving home.
在倾角α=30°斜面上有一块竖直放置的档板,在档板和斜面之间放有一个重为G=20N的光滑圆球,如图,试求这个球对斜面的压力和对档板的压力.
化简:
(1)(2a+3b)(3a﹣2b)﹣12(3a+2b)2﹣a(32a﹣b);
(2)4-aa÷(a+2a2-2a﹣a-1a2-4a+4