解：
(x²y-4y³)/x²+4xy+4y²)·[4xy/(x-2y)+x]=(x²y-4y³)/(x+2y)²*(4xy+x²-2xy)/(x-2y)=y(x+2y)(x-2y)/(x+2y)²*x(x+2y)/(x-2y)=xy=(√2-1)(√2+1)=(√2)²-1
=2-1=1
担心你手机显示不了平方符号，图片格式为
