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已知:x-2的平方根是±2, 2x+y+7的立方根是3,求 x2+y2 的平方根.
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解:因为4的平方根是±2 ,所以 x-2=4,得到x=6,因为27的立方根是3,所以 2x+y+7=27,得到y=4,代入可得x2+y2=62+42=52

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                                                                                爱与孤独
      ①爱和孤独是人生最美丽的两支曲子,两者缺一不可。没有爱的心灵会孤独,未曾体味过孤独的人也不可能懂得爱。由于怀着爱的希望,孤独才是可以忍受的,甚至是甜蜜的。
      ②不止—位先贤指出,—个人无论看到怎样的美景奇观,如果他没有机会向人讲述,他就决不会感到快乐。人终究是离不开同类的。一个无人分享的快乐绝非真正的快乐,而一个无人分担的痛苦则是最可怕的痛苦。所谓分享和分担,未必要有人在场。但至少要有人知道。永远没有人知道,绝对的孤独,痛苦便会成为绝望,而快乐——同样也会变成绝望!
      ③交往为人性所必需,人生之常态,而它的分寸却不好掌握。帕斯卡尔说:“我们由于交往而形成了精神和感情,但我们也由于交往而败坏着精神和感情。”我相信,前—种交往是两个人之间的心灵沟通,它是马丁•布伯所说的那种“我与你”的相遇,既充满爱,又尊重孤独;相反,后一种交往则是熙熙攘攘的利害交易,它如同尼采所形容的“市场”,既亵渎了爱,又羞辱了孤独。相遇是人生莫大的幸运,在此时刻。两颗灵魂仿佛同时认出了对方,惊喜地喊出:“是你!”人一生中只要有过这个时刻,爱和孤独便都有了着落。

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    Language students often think they have memory problems. They worry because they can't remember words. In fact, the problem usually isn't with their memory. The problem is with how they study.

    To remember words better, you need to understand how memory works. There are two kinds of memories: short-term and long-term. When you see, hear, or read something, it goes first into short-term memory. But short-term memory lasts for only a few seconds. You will only remember something longer if it goes into long-term memory. Your long-term memory is like a very big library with many, many books. And like a library, it's organized (有条理的). When you put away a book – or memory – you can't just leave it anywhere. You have to choose a place where you can find it again.

    How can you do this with vocabulary? The answer is to work with the word and think about the word in new ways. You can do this by writing new sentences that include it. Even better, you can invent a little story about the word, with people or places that you know. Another way is to make a picture in your mind with the word. For example, if the word is height, you can think of the tallest person you know and try to guess his or her height. All of these activities are good ways to think about words. They make the meaning of words stronger in your long-term memory. And they give a way to find a word when you need it.