請用配方解下列各式：
A} 2x ^2 - x = 15
B} 3x ^2 - x- 4 =0
Thank you very much!!
F.4 配方法
2007-06-08 6:17 am
回答 (2)
2007-06-08 6:24 am
✔ 最佳答案
2x^2 - x = 152(x^2 - x/2) = 15
2(x^2 - x/2 + 1/16) = 15 + 1/8
2(x - 1/4)^2 = 121/8
(x - 1/4)^2 = 121/16
x - 1/4 = 11/4 or x - 1/4 = -11/4
x = 3 or x = -5/2
3x^2 - x- 4 =0
3(x^2 - x/3) - 4 = 0
3(x^2 - x/3 + 1/36) - 4 - 1/12 = 0
3(x - 1/6)^2 = 49/12
(x - 1/6)^2 = 49/36
x - 1/6 = 7/6 or x - 1/6 = -7/6
x = 4/3 or x = -1
2007-06-08 6:23 am
2x ^2 - x = 15
(2x+5)(x-3)=0
x=-2.5or3
3x ^2 - x- 4 =0
(3x-4)(x+1)=0
x=4/3or-1
(2x+5)(x-3)=0
x=-2.5or3
3x ^2 - x- 4 =0
(3x-4)(x+1)=0
x=4/3or-1
參考: me
收錄日期: 2021-04-13 00:50:11
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https://hk.answers.yahoo.com/question/index?qid=20070607000051KK04492