已知2log3[(x—y) / 2]=log3(xy),则x / y=_________.
问题描述：
已知2log3[(x—y) / 2]=log3(xy),则x / y=_________.
答
[(x-y)/2]^2=xy
x^2-2xy+y^2=4xy
x^2-6xy+y^2=0
(x/y)^2-6(x/y)+1=0
x/y=3+2*2^0.5或者3-2*2^0.5