f(x)有二阶连续导数大于0F(0)=F#39;(0)=0u是f(x)在（x,f(x)）处切线在x轴截距,求lim（x→0）xf(u)/uf(x)
<p>问题：f(x)有二阶连续导数大于0F(0)=F#39;(0)=0u是f(x)在（x,f(x)）处切线在x轴截距,求lim（x→0）xf(u)/uf(x)<p>答案：↓↓↓<p class="nav-title mt10" style="border-top:1px solid #ccc;padding-top: 10px;">彭宏韬的回答：<div class="content-b">网友采纳 由题可知,f(x)=ax²+o(x²) u=x-f(x)/f'(x) limu/x=lim 而limf(x)/xf'(x)=limf'(x)/=limf''(x)/=f''(0)/(2f''(0)+0)=1/2,所以limu/x=1/2 且limf(u)/f(x)=lim/=limu²/x²=1/4 所以原式=/(limu/x)=1/2
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