用配方法求解二次方程
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0:00 - 0:02在这段视频中，我将向你们展示一种技巧
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0:03 - 0:09叫做配方法。
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0:09 - 0:14它的奇妙之处在于它适用于任何二次方程，
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0:14 - 0:18它实际上是
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0:18 - 0:19二次方程的基。
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0:19 - 0:22在下个或者在那之后的视频，
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0:22 - 0:26我会用配方法来证明这个二次公式。
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0:26 - 0:28但在此之前，我们需要理解。
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0:28 - 0:29它到底是怎么回事。
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0:29 - 0:32这是建立在上一集视频基础上的，
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0:32 - 0:34我们用完全平方
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0:34 - 0:36求解了二次方程。
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0:36 - 0:40已知二次方程x² - 4x
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0:40 - 0:45等于5。
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0:45 - 0:47我在这里放这么大的空间是有原因的。
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0:47 - 0:50在上一集视频中，我们知道
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0:50 - 0:53如果左边是完全平方，
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0:53 - 0:56就可以很直接地求解出来。
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0:56 - 0:59你看，配方就是把二次方程变成完全平方，
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0:59 - 1:02对它进行工程处理，
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1:02 - 1:04两边加减
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1:04 - 1:06使它变成完全平方。
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1:06 - 1:08我们该怎么做呢?
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1:08 - 1:10为了使左边是完全平方的，
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1:10 - 1:13这里必须有某个数。
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14:02 - 14:04
- Title:
- 用配方法求解二次方程
- Description:
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more » « less
- Video Language:
- English
- Team:
Khan Academy
- Duration:
- 14:06
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Ziye_Liao edited Chinese, Simplified subtitles for Solving Quadratic Equations by Completing the Square | |
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Ziye_Liao edited Chinese, Simplified subtitles for Solving Quadratic Equations by Completing the Square | |
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Ziye_Liao edited Chinese, Simplified subtitles for Solving Quadratic Equations by Completing the Square | |
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Ziye_Liao edited Chinese, Simplified subtitles for Solving Quadratic Equations by Completing the Square | |
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Ziye_Liao edited Chinese, Simplified subtitles for Solving Quadratic Equations by Completing the Square | |
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Ziye_Liao edited Chinese, Simplified subtitles for Solving Quadratic Equations by Completing the Square |