计算$\frac{a^2-16}{2a+8}$=____ 

如图是一个几何体的三视图，其中主视图与左视图都是边长为4的等边三角形，则这个几何体的侧面展开图的面积为____.

    Elephants are the largest living animals on land. More than 500 1 kinds of elephants were found on the earth over the last 55 million years. Only 2 kinds are still alive today: the African elephant and the Asian (or Indian) elephant. These elephants can only be found in 3 places. However, the older kinds lived in cold places a long time4. An example is the mammoth (猛犸象) — the largest hairy elephant.

    The mammoth was the largest living elephant, which was about seven tons. 5 the elephants today, mammoths had black or dark brown hairs 6their bodies. All the mammoths had tusks (长牙).

    Scientists found most of the extinct (灭绝的) animals by 7 the fossils, 8 their bones and teeth that could be found. However, mammoths are quite different. During the Ice Age, mammoths died and were covered 9 in the ice. The ice kept them very well. So scientists could find the 10 body of the mammoth.

儒家认为：‘乐者为同，礼者为异。同则相亲，异则相敬。乐胜则流，礼胜则离。合情饰貌者，礼乐之事也。礼义立，则贵贱等矣。乐文同，则上下和矣。”据此，礼乐的主要社会功能是（    ）