作者suker (..)
看板Math
标题Re: [中学] 解三元二次方程
时间Wed Mar 2 19:14:12 2011
※ 引述《haolihy (好厉害)》之铭言:
: p* (x+y) =221
: p* (1+x^2) =281
: p* (1+y^2) =209
: 求x, y, p ?
p* (x+y) =221 -----------------(1)
p* (1+x^2) =281 -----------------(2)
p* (1+y^2) =209 -----------------(3)
(2)-(3) p(x-y)(x+y)
--------- = ------------------- = 72/221
(1) p(x+y)
x-y =72/221
x=y+72/221
1+(y+72/221)^2
(2)/(3) ==> -------------------- =281/209
1+y^2
1+y^2 + 2(72/221)y+ (72/221)^2 = 281/209 (1+y^2)
72y^2/209 -144y/221 + 2433096/10207769 =0
代公式 y=0.495754 或 1.39565
选(1)/(3)比较好看点
(2y+72/221)/(1+y^2) =221/209
主要数字出得好丑
带回
{x,y,p} ={0.8215 , 0.49575 , 167.767}
{x,y,p} ={1.72144 , 1.39565 , 70.8995}
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◆ From: 118.169.82.226
※ 编辑: suker 来自: 118.169.82.226 (03/02 19:18)
1F:推 n19860423 :真的好丑..原本要算,但太丑就开始怀疑数字有没有错 03/02 19:17