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应是一个条件极值问题
应物坦是 b+2c+λbc=0(1), a+2c+λac=0(2),
2a+2b+λab=0(3), abc=k(4), k是已知的,求a、b、c、λ。
(1)即 b+2c = -λbc (5),
(2)即 a+2c = -λac (6),
(3)即 2a+2b = -λab (7)
(5)/(6) , 得 a = b
(5)/(7) , 得 a = 2c
代入(4)得纳蚂银 2c·2c·c = k, c = (k/4)^(1/3),
a = b = 2(k/洞宴4)^(1/3)
应物坦是 b+2c+λbc=0(1), a+2c+λac=0(2),
2a+2b+λab=0(3), abc=k(4), k是已知的,求a、b、c、λ。
(1)即 b+2c = -λbc (5),
(2)即 a+2c = -λac (6),
(3)即 2a+2b = -λab (7)
(5)/(6) , 得 a = b
(5)/(7) , 得 a = 2c
代入(4)得纳蚂银 2c·2c·c = k, c = (k/4)^(1/3),
a = b = 2(k/洞宴4)^(1/3)
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