作者micron (想閉關可是門關不起來)
看板GMAT
標題Re: [計量]PP兩題
時間Tue Jan 1 21:13:15 2008
※ 引述《Jinai (橘子汽水好喝~)》之銘言：
: 167. 17541-!-item-!-187;#058&011147
: If x is positive, which of the following could be the correct ordering of
: X^(-1),2X and X^2
: (I) X^2<2X<X^(-1)
: (II) X^2<X^(-1)<2X
: (III)2X<X^2<X^(-1)
: 答案是(I)&(II)
: 但是我只解出來(I)
: 請問要如何解(II)
: 謝謝
I was wondering whether (II) is wrong.
Let's see... in three cases
(1) If X is quite small, such as 0.00001
Certainly, their relation is (I)
(2) If 1<X<2
Their relation will be
X^(-1) < X^2 < 2X. For example, you can subsitute
X with 1.5, you can get 0.666666 < 2.25 < 3
(3) If X>2
It would be X^2 > 2X > X^(-1)
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※ 編輯: micron 來自: 123.195.155.25 (01/01 21:13)