Re: [微積] 至少一解
※ 引述《stman (小強)》之銘言：
: 2
: For what value of C does the equation ln x=Cx have exactly one solution?
如交點y座標 > 0
(lnx)' = 1/x
(Cx^2)' = 2Cx
當1/x = 2Cx 有重根的時候
=> x^2 = 1/(2C)
=> x = 1/sqrt(2C) > 0 => C > 0
且 ln(1/sqrt(2C)) = C/(2C) = 1/2
=> C = 1/2e
除了這個解
C <=0也符合
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