coordinate geometry(circle)

2010-04-03 3:19 am

find the equation of the circle through the points (1,-4) and (5,2), and has its centre on the line x-2y+9=0.

ans: x^2+y^2+6x-6y-47=0

更新1:

re: nelsonywm2000, why can i let the centre be(2t-9, t)??

回答 (1)

2010-04-03 3:35 am

✔ 最佳答案

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圖片參考：http://img69.imageshack.us/img69/9866/26589513.png

2010-04-02 19:35:10 補充：
http://img69.imageshack.us/img69/9866/26589513.png

2010-04-02 21:33:29 補充：
先隨意設y=t
x-2t+9=0=> x=2t-9
也可設x=t,
t-2y+9=0=>y=(t+9)/2然後計算結果也會是一樣

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