当销售单价定为x元时,每千克利润是(x-40)元,销售单价的上涨了(x-50)元,月销售量减少了10(x-50)千克,这时的销售量是500-10(x-50)千克,月销售利润是y=(x-40)[500-10(x-50)]=(x-40)(500-10x+500)=(x-40)(-10x+1000)=-10...