26日考, 急问几道本月数学机经!!!

tonywear · 发表于 2003-12-24 21:49:00

1.Xn+1=2(Xn-1)-1 ，X1=2，问X20-X19
seems an old JJ, forget how to resolve it.

2.DS: N is square of an integer?
I N is the cube of an integer,
II N is the square root of an integer
E

3.N不等於0， 2^N/3 余数为1，下面哪个对？(N is a nonzero integer, and 1 is the remainder of 2^N divided by 3. Which of the following is right?)
1, N>0
2, 3^N=(-3)^N
3, 根号下(2^N) 是整数
(1) only 1
(2) only 2
(3) 1&2
(4) 1&3
(5)2&3

1 and 2 and 3 all right

4.某车行有full-size车31辆，mid-size 19辆，compact 10辆，并有红白蓝三种颜色，问红色full-size多少辆。(C)
a) mid-size和compact没有红车
b) 红车比白车和蓝车的总和还多
Maybe 31 or 30, so E

[此贴子已经被作者于2003-12-24 21:51:56编辑过]

donna · 发表于 2003-12-24 22:05:00

以下是引用tonywear在2003-12-24 21:49:00的发言：

1.Xn+1=2(Xn-1)-1 ，X1=2，问X20-X19
seems an old JJ, forget how to resolve it.

抱歉你的等式写的不明白，Xn+1是第N项加1，还是第N+1项啊？
麻烦写明白，否则不好做啊！

whitedeer · 发表于 2003-12-24 23:37:00

4.某车行有full-size车31辆，mid-size 19辆，compact 10辆，并有红白蓝三种颜色，问红色full-size多少辆。(C)
a) mid-size和compact没有红车
b) 红车比白车和蓝车的总和还多
Maybe 31 or 30, so E

should be c.

tonywear · 发表于 2003-12-25 13:04:00

another one:

一地区,共有ABCE四个区块,250个ZIP code,a区块的邮政编码数是B区的2/1,C区的1/1,D区的4/3, A 区共有125000人,25%买了某产品,问A区的每个邮政编码范围内有多少人买产品? 答:算出A 区的邮政编码数去除产品数.
406.25
my answer is 2000/3

tonywear · 发表于 2003-12-25 13:06:00

他原题就这样呀,谁能找到该题目的老JJ.

donna · 发表于 2003-12-25 14:02:00

以下是引用tonywear在2003-12-25 13:06:00的发言：
他原题就这样呀,谁能找到该题目的老JJ.

别着急，我记得此题可以通过前面几项的规律，得出一个通项的。不会很难，别担心！

lyle · 发表于 2003-12-25 16:31:00

以下是引用tonywear在2003-12-24 21:49:00的发言：
3.N不等於0， 2^N/3 余数为1，下面哪个对？(N is a nonzero integer, and 1 is the remainder of 2^N divided by 3. Which of the following is right?)
1, N>0
2, 3^N=(-3)^N
3, 根号下(2^N) 是整数
(1) only 1
(2) only 2
(3) 1&2
(4) 1&3
(5)2&3

1 and 2 and 3 all right

2中，如果n是奇数，3^n是正数, 3^n是负数.

[此贴子已经被作者于2003-12-25 16:33:06编辑过]

wanze · 发表于 2003-12-25 16:56:00

1.Xn+1=2(Xn-1)-1 ，X1=2，问X20-X19
seems an old JJ, forget how to resolve it

the answer is (2^17)*3

wanze · 发表于 2003-12-25 17:04:00

1.Xn+1=2(Xn-1)-1 ，X1=2，问X20-X19
seems an old JJ, forget how to resolve it

the answer is (2^17)*3

model · 发表于 2003-12-25 21:14:00

4.某车行有full-size车31辆，mid-size 19辆，compact 10辆，并有红白蓝三种颜色，问红色full-size多少辆。(C)
a) mid-size和compact没有红车
b) 红车比白车和蓝车的总和还多
Maybe 31 or 30, so E

should be c.

为什么，明明31，30都可以呀？

TO LYLE:
2中，如果n是奇数，3^n是正数, 3^n是负数.

问题：2中n不可能是负数的呀？

26日考, 急问几道本月数学机经!!!

26日考, 急问几道本月数学机经!!!

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