※ 引述《joewusuper (阿吉)》之铭言： : 题目一: 这题不懂题目到底要我求什麽，也完全无法列式 : 　　　　麻烦大家帮忙一下。　 : An investor buy one share of stock for 100. : If the share price change as follows : (measured relative to the prior day's price): : Day 1 Up 30% : Day 2 Down 15% : Day 3 Unchanged : Day 4 Chang r% : Day 5 Down 10% : If the pattern of relative price movements observed : on the first 5 days is repeated indefinitely, : how will the price of the share of stock behave in the long run? lim ( 1.3 * 0.85 * 1 * (1+r%) * 0.9 )^n n->∞ lim ( 0.9945 * (1+r%) )^n n->∞ 考虑 0.9945 * (1+r%) = 1 => r % = 1/0.9945 - 1 = x let if r > x , 爆掉 r = x , 维持原价 r < x , 跑到 0 : 题目二：麻烦大家告诉我，用什麽观念下去求比较快 : A company has 120,000 to spend on the development and promotion : of a new product. The past experience indicates : that if x is spent on development and y is spent on promotion, : then X^(1/2)*Y^(3/2)/30,000*3^(3/2) items can be sold. : (a) To maximize the number of items sold, : how much money should be spend on development. : (b) What is the maximum number of items can be sold? 先知到 x + y = 120000 然後目标是 那数字，分母是常数不管~ 去考虑 x * y^3 的极值 ( 最後再开根号即可 ) 因为 x . y 都大於等於零 利用算几 x + (y/3) + (y/3) + (y/3) 4 --------------------------- >= √[(x * y^3)/27] 4 ... 等号会发生在 x = y/3 的地方~ 这样条件应该就都有了:) : 感谢各位的解答罗!! : 如果题目有不清楚我附上网址 : http://www.acad.scu.edu.tw/1/entrance/98exam/DE/95.pdf : 里面的3.4题~ --

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