2lg((x－y)/2)＝lg x＋lg y有意义,则需x-y>0,x>0,y>0 x/y>1原式可化为：lg((x-y)/2)^2=lg(xy)∴(x-y)²/4=xy∴x²-2xy+y²=4xyx²-6xy+y²=0两边同时除以y²(x/y)²-6(x/y)+1=0 用求根...