利用配方法解二次方式
回答 (1)
2009-02-12 7:51 am
✔ 最佳答案
2x2 - √5x - 30 = 0
2[x2 - (√5)x/2] - 30 = 0
2[x2 - 2(√5/4)x + (√5/4)2] - 2(√5/4)2 - 30 = 0
2[x - (√5/4)]2 - (25/8) - 30 = 0
[x - (√5/4)]2 - (25/16) - 15 = 0
[x - (√5/4)]2 = (265/16)
x - (√5/4) = √(265)/4 ooro x - (√5/4) = -√(265)/4
x = (√5 + √265)/4 ooro x = (√5 - √265)/4
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收錄日期: 2021-04-29 18:17:36
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https://hk.answers.yahoo.com/question/index?qid=20090211000051KK02143