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OMC227

OMC227(C)

 解と係数の関係より,x1+x2++x100=4x_1+x_2+\cdots+x_{100}=-4 が成り立つ.また,x100+4x9913=0x^{100}+4x^{99}-13=0x0x\neq 0 のとき x+413=1x99\dfrac{x+4}{13}=\dfrac{1}{x^{99}} と変形できるので, i=1100j=1100xixj99=(i=1100xi)(j=11001xj99)=(i=1100xi)(j=1100xj+413)=(4)4+4×10013=158413\begin{aligned} \sum_{i = 1}^{100}\sum_{j = 1}^{100}\frac{x_i}{x_j^{99}} & = \Bigg(\sum_{i = 1}^{100} x_i\Bigg)\Bigg(\sum_{j = 1}^{100} \frac{1}{x_j^{99}}\Bigg)\\ & = \Bigg(\sum_{i = 1}^{100} x_i\Bigg)\Bigg(\sum_{j = 1}^{100} \frac{x_j+4}{13}\Bigg)\\ & = (-4)\cdot\frac{-4+4\times100}{13} \\ & = -\frac{1584}{13} \end{aligned} と計算できる.よって解答すべき値は 1597\textbf{1597} である.

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