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분류
아무 수학 공식이나 적어보세요. 수식 문법을 테스트하기 위해 만든 문서입니다.

f(x)=(x+x++xx  times)=limh 0{(x+h)+(x+h)++(x+h)(x+h)  times}(x+x++xx  times)h=limh 0(h+h++h)x  times+{(x+h)+(x+h)++(x+h)h  times}h=x+limh 0(xh+h2)h=x+x=2x\begin{aligned}f'(x)&=(\overbrace{x+x+ \cdots +x}^{x\;\rm{times}})'\\&= \displaystyle\lim_{h \to \ 0} \frac {\{\overbrace{(x+h)+(x+h)+ \cdots +(x+h)}^{(x+h)\;\rm{times}}\} - (\overbrace{x+x+ \cdots +x}^{x\;\rm{times}})}{h}\\&= \displaystyle\lim_{h \to \ 0} \frac {(\overbrace{h+h+ \cdots +h)}^{x\;\rm{times}} + \{\overbrace{(x+h)+(x+h)+ \cdots +(x+h)}^{h\;\rm{times}}\}}{h}\\&=x +\displaystyle\lim_{h \to \ 0} \frac{(xh+h^2)}{h}\\&=x+x=2x\end{aligned}

limxaf(x)=L\displaystyle \lim_{ x \rightarrow a }{ f ( x ) } = L