x的平方-y的平方分之x的平方+2xy+y的平方除一x-y分之x的平方+xy,其中x=√2-1,y=√2+1
=(x+y)^2/(x+y)(x-y) /((x^2+xy)/(x-y))
=(x+y)/(x-y) * (x-y)/x(x+y)
=1/x
=1/(√2-1)
=√2+1