作者LuisSantos (^______^)
看板trans_math
标题Re: [微分]
时间Thu Jan 25 01:04:35 2007
※ 引述《king911015 (早已放弃爱上你)》之铭言：
: For what value or values of the constant K will the curve
: y=X^3+kX^2+3X-4 have exactly one horizontal tangent?
令 y = f(x) = x^3 + kx^2 + 3x - 4
则 f'(x) = 3x^2 + 2kx + 3
因为 y = f(x) = x^3 + kx^2 + 3x - 4 恰有一条水平切线
所以 f'(x) 的判别式等於0
(2k)^2 - (4)*(3)(3) = 0
k^2 - (3)*(3) = 0
k^2 = 3*3 => k = 3 或 -3
: Suppose a,b are constants such that lim sin2x a
: x->0 (------- + ---- + b )=0
: x^3 x^2
: then a+b =?
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