作者catspace (柏拉图的永恒...)
看板GMAT
标题Re: [计量] GWD19-2,9
时间Thu Oct 9 11:59:35 2008
※ 引述《chilis (庞克新生报到^_^)》之铭言：
: Q2:
: For which of the following functions f is f(x) = f(1-x) for all x?
: A. f(x) = 1 - x
: B. f(x) = 1 - x2
: C. f(x) = x2 - (1-x)2
: D. f(x) = x2(1-x)2
: E. f(x) = x / (1-x)
: ----------------------------------------------------------------------------------------------------------------------
: Answer: D 不懂题目??
(A) f(1-x) = 1-(1-x) = x 不等於 f(x)
(B) f(1-x) = 1-(1-x)^2 = 2x - x^2 不等於 f(x)
(C) f(1-x) = (1-x)^2 - [1-(1-x)]^2 = 1-2x 不等於 f(x)
(D) f(1-x) = (1-x)^2 * [1-(1-x)]^2 = (1-x)^2 * x^2 等於 f(x)
(E) f(1-x) = (1-x)/[1-(1-x)] = (1-x)/x 不等於 f(x)
答案D
: Q9:
: A certain computer program generates a sequence of numbers a1, a2, … ,
: a n such that a1 = a2 = 1 and ak = ak-1 + 2ak-2 for all integers k such that
: 3 ? k ? n. If n > 6, then a7 = ?
: A. 32
: B. 43
: C. 64
: D. 100
: E. 128
: ----------------------------------------------------------------------------------------------------------------------
: Answer: B
: a1 =a0+2a-1=1
: a2 =a1+2a0= 1
: a3=a2+2a1=1+2*1=3=2^1+1
: a4=a3+2a2=3+2*1=5=2^2+1
: a5=a4+2a3=5+2*3=11
: a6=a5+2a4=11+2*5=21
: a7=a6+2a5=21+2*11=43
: 找不出规则变化,有快速解法吗?
: 感谢:)
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