设商场计划投资x元,在月初出售共获利y1元,在月末出售共获利y2元,根据题意,得
y1=15%x+（x+15%x）·10%=0.265x,
y2=30%x-1050=0.3x-700.
∴y1-y2=0.265x-(0.3x-1050)=1050-0.035x.
①当y1-y2=0时,有1050-0.035x=0,∴x=30000.
∵当x=30000时,两种销售方式获利一样多.
②当y1-y2＞0时,有1050-0.035x＞0,∴x＜30000.
∴当x＜30000时,y1＞y2.即月初出售获利较多.
③当y1-y2＜0时,有1050-0.035x＜0,∴x＞30000.
∴当x＞30000时,y1＜y2.即月末出售获利较多.
最好在算一遍,以免数据有错!