∵P=100-QdP=d(100-Q)dP=d100-dQ.dP=0-dQ.【常数的导数或微分等于零】dP=-dQ.【这是微分的写法】,两边同除以dQ得到：∴dP/dQ=-1.若按求导的写法应该是：【Q---看成自变量,P---为函数】P'=dP/dQ=(100-Q)'=100'-Q'dP/d...