20/11/02 18:39:47.18 nV+GRV6y.net
>>492
l(x) = x + √(7+xx),
m(x) = √(9-xx) + √(18-xx),
これより
l' /l = 1/√(7+xx)
m' /m = - x/√((9-xx)(18-xx))
Max.条件より
0 = S'(x)
= (l･m)'
= l'･m + l･m'
= l･m(l' /l + m' /m)
= l･m{1/√(7+xx) - x/√((9-xx)(18-xx))},
∴ xx (7+xx) = (9-xx) (18-xx),
∴ xx = 81/17,
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