解析
x=√2+1
y=√2-1
(x²-y²)/(x²+2xy+y²)
=(x-y)(x+y)/(x+y)²
=(x-y)/(x+y)
将x y代入
=（√2+1-√2+1）/(√2+1+√2-1)
=2/2√2
=√2/2