We present an optimal version of Descartes' rule of signs to bound the number of positive real roots of a sparse system of polynomial equations in n variables with n+2 monomials. This sharp upper bound is given in terms of the sign variation of a sequence associated to the exponents and the coefficients of the system.

翻译：我们提出了一个理想版本的笛卡尔标志规则,以将n变量中的稀有多面方程式系统的实际正根数与n+2单面方程式捆绑在一起。这个尖锐的上层框是用与指数和该体系系数相关的序列的符号变异来表示的。