问题
问答题
没一物体占有空间区域Ω={(x，y，z)|0≤x≤2，0≤y≤1，0≤z≤3}，该物体在点(x，y，z)处的密度为ρ(x，y，z)=x+2y+z，求这个物体的质量．
答案
参考答案：
解析：由题意知
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没一物体占有空间区域Ω={(x，y，z)|0≤x≤2，0≤y≤1，0≤z≤3}，该物体在点(x，y，z)处的密度为ρ(x，y，z)=x+2y+z，求这个物体的质量．
参考答案：
解析：由题意知
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| Have you ever had to decide whether to go shopping or stay home and watch TV on a weekend? Now you 1 do both at the same time. Home shopping television networks (网络) have become a 2 for many people to shop without 3 having to leave their homes. Some shoppers are 4 of department stores and supermarkets- 5 the crowds, waiting in long lines, and sometimes 6 of finding anything they want to buy. They'd rather sit quietly at home in front of the TV set and 7 a friendly announcer describe a product 8 a model shows it. And they can 9 around the clock, buying something 10 by making a phone call. Department stores and even mail-under companies are 11 to join in the success of home shopping. Large department stores are busy 12 their own TV channels (频道) to encourage TV shopping in the future. 13 can ask questions about products and place 14 , all through their TV sets. Will shopping by television 15 take the place of shopping in stores? Some industry managers think so. 16 many people find shopping at a 17 store a great enjoyment. And for many shoppers, it is still important to 18 or try on dresses they want to buy. That's 19 specialists say that in the future, home shopping will 20 together with store shopping but will never entirely replace (取代) it. | ||||
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