设售价是每个x元,x﹥100,则每个利润是(x-90)元,售价上涨了(x-100)元,少卖了10(x-100)个,实际卖出[500-10(x-100)]个,根据题意,有方程(x-90)[500-10(x-100)]=9000(x-90)(1500-10x)=9000(x-90)(150-x)=900150x-x²-...