※ 引述《joewusuper (阿吉)》之銘言：
: 題目一: 這題不懂題目到底要我求什麼，也完全無法列式
: 麻煩大家幫忙一下。
: 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->∞
考慮 0.9945 * (1+r%) = 1
=> r % = 1/0.9945 - 1 = x
let
if r > x , 爆掉
r = x , 維持原價
r < x , 跑到 0
: 題目二：麻煩大家告訴我，用什麼觀念下去求比較快
: 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
然後目標是 那數字，分母是常數不管~
去考慮 x * y^3 的極值 ( 最後再開根號即可 )
因為 x . y 都大於等於零 利用算幾
x + (y/3) + (y/3) + (y/3) 4
--------------------------- >= √[(x * y^3)/27]
4
...
等號會發生在 x = y/3 的地方~
這樣條件應該就都有了:)
: 感謝各位的解答囉!!
: 如果題目有不清楚我附上網址
: http://www.acad.scu.edu.tw/1/entrance/98exam/DE/95.pdf
: 裡面的3.4題~
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