来自《耶鲁大学开放课程：博弈论 第22集 第22集》

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  So to work out what X is what I'm going to do is
  想要求X的值
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  I'm going to multiply X by delta,
  就要先把X乘以δ
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  so what's deltaX?
  δX是多少呢
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  So this 2 here will become a 2delta,
  这里的2变成了2δ
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  and this delta2 here will become a delta squared 2,
  而这里的2δ就变成了2乘δ平方
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  and this delta squared 2 will become a delta cubed2,
  而这个2乘δ平方变成2乘δ立方
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  and this delta cubed 2 will become a delat42, and so on.
  2乘δ立方变成2乘δ四次方 以此类推
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  Now what I'm going to do is I'm going to
  接下来我们再来
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  subtract the second of those lines from the first of those lines.
  用第二行减第一行
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  So what I'm going to do is, I'm going to subtract X--deltaX.
  即把X减去δX
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  So I'm going to subtract the second line from the first line.
  所以我把第二行减掉第一行
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  And when I do that I'm going to notice I hope that
  这样我就会发现