四、设函数 y=f(x) 的二阶可导,且 '(x)gt 0 (0)=0, '(0)=0, 求-|||-lim _(xarrow 0)dfrac ({x)^3f(u)}(f(x){sin )^3u} 其中u是曲线 y=f(x) 上点p(x,f(x))处的切线在x轴上的截距.

3.设f(x)在 =O 的邻域内二阶可导,且 (0)=0,-|||-(0)=2, 求-|||-lim _(xarrow 0)dfrac (f(x)-f[ ln

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1．设f(x)在x=0处可导，且f(0)=0,则lim _(xarrow 0)dfrac (f(3x)-f(x))(x)-|||-__=______.1．设f(

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154 设 lim _(xarrow {x)_(0)^+}f(x)=lim _(xarrow {x)_(0)^-}(x)=a, 则-|||-(A)f(x)在 =