※ 引述《hansonJu (eric)》之銘言：
: 2x+A(2x+8y)=0
: 2x+A(8x+14y)=0
: x^2+7y^2+8xy-225=0 求x,y分別是多少 怎麼算?
(解)
2x+A(2x+8y)=0 (1)
2x+A(8x+14y)=0 (2)
x^2+7y^2+8xy-225=0 (3)
(2)-(1) : A(6x+6y)=0
(a) A = 0
from (1) => x=0 insert into (3)
15 15
=> 7y^2-225 =0 => y = ------- , - -------
7^1/2 7^1/2
(b) A \= 0
=> 6x+6y=0 => x=-y insert into (3)
x^2 + 7x^2 - 8x^2 -225 = 0
=> -225 = 0 not exist !
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