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gaojinye 发表于 2009-9-11 03:07

请教一道数学题

[font=Times New Roman][size=3]For any integers [i]x[/i] and [i]y[/i], min([i]x[/i], [i]y[/i]) and max([i]x[/i],[i] y[/i]) denote the minimum and the maximum of [i]x[/i] and [i]y[/i], respectively.
For example, min(5, 2) = 2 and max(5, 2) = 5.
For the integer [i]w[/i], what is the value of min(10, [i]w[/i]) ?[/size][/font]

[font=Times New Roman][size=3](1)

[i]w[/i] = max(20, [i]z[/i]) for some integer [i]z[/i].[/size][/font]
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[i]w[/i] = max(10, [i]w[/i])[/size][/font]
[font=Times New Roman][size=3]                   [/size][/font]
[font=Times New Roman][size=3]A. Statement (1) [b]ALONE[/b] is sufficient, but statement (2) alone is not sufficient.[/size][/font]
[font=Times New Roman][size=3]B. Statement (2) [b]ALONE[/b] is sufficient, but statement (1) alone is not sufficient.[/size][/font]
[font=Times New Roman][size=3]C. [b]BOTH [/b]statements [b]TOGETHER[/b] are sufficient, but [b]NEITHER[/b] statement [b]ALONE[/b] is sufficient.[/size][/font]
[font=Times New Roman][size=3]D. [b]EACH[/b] statement [b]ALONE[/b] is sufficient.[/size][/font]
[font=Times New Roman][size=3]E. Statements (1) and (2) [b]TOGETHER[/b] are [b]NOT[/b] sufficient.[/size][/font]
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[font=Times New Roman][size=3]答案是D,但我认为条件（1）不一定满足，因为并没说z不等于w，z=w时就无法判断了，我这么说对么？[/size][/font]
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JJJooe 发表于 2009-9-11 07:23

答案的确是D么
条件一：无论z为何值，w=max（20，z）肯定是大于等于20的一个值
所以 min(10, w)=10

Orchidz 发表于 2010-2-6 15:45

这里（1）里的for some integer z有什么讲究呢？

这里（1）里的for some integer z有什么讲究呢？是不是意味着w=max(20,z)不总是成立？

JJJooe 发表于 2010-2-6 23:43

回复 3# Orchidz 的帖子

不太懂你的意思
for some integer z就是说z是整数么

Orchidz 发表于 2010-2-9 10:47

哦，酱紫啊~ 想多了。。。

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