问题描述: 若(x+y-5)^2+lx-y+3l=0x^2-y^2=? 1个回答 分类:数学 2014-11-13 问题解答: 我来补答 因为 (x+y-5)^2 >=0, lx-y+3l >=0, (x+y-5)^2+lx-y+3l=0所以 (x+y-5)^2 =0, lx-y+3l =0所以 x+y = 5, x-y = -3所以 x^2-y^2 = (x+y)*(x-y) = -15 展开全文阅读