原式=x²/[xy(x+y)]-y²/[xy(x+y)]
=(x²-y²)/[xy(x+y)]
=(x+y)/(x-y)/[xy(x+y)]
=(x-y)/(xy)
=[(√2+1)-(√2-1)]/[(√2+1)(√2-1)]
=(√2+1-√2+1)/(√2²-1²)
=2/(2-1)
=2