中四一元二次方程---10點---thx

2008-02-06 8:20 am

已知二次方程ax^2-7x+2=0的其中一個根是2，求a
---10點---thx

回答 (4)

2008-02-06 8:31 am

✔ 最佳答案

代２入ｘ
a(2)^2-7(2)+2=0
4a-14+2=0
4a=12
a=3

參考: 自己

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2008-02-06 9:09 am

a(2^2) - 7(2) + 2 = 0
4a -14 + 2 = 0
4a = 14 - 2
4a = 12
a = 3

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2008-02-06 8:30 am

When x=2, then
a(2^2) - 7(2) + 2 = 0
4a -14 + 2 = 0
4a = 14 - 2
4a = 12
a = 3
Hope you understand

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2008-02-06 8:29 am

最簡單的方法是將數根直接代入數式之中，即

4a - 14 + 2 = 0
4a - 12 = 0
4a = 12
a = 3

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