问题描述: 设x>0,y>0,且(x-1)(y-1)≥2,则xy的取值范围为? 1个回答 分类:数学 2014-09-21 问题解答: 我来补答 (x-1)(y-1)≥2xy-(x+y)+1≥2xy≥1+x+y 1)xy≥1+√(x^2+y^2+2xy)xy-1≥√(x^2+y^2+2xy)(xy)^2-2xy+1≥x^2+y^2+2xy>=4xy(xy)^2-6xy+1≥0xy≥3+2√2或xy≤3-2√2由1)得xy>1所以xy≥3+2√2 展开全文阅读