反证法.假设存在既约分式m/n满足√x + √y = m/n,那么移项可得√x = m/n - √y,两边平方得x = m²/n² + y - 2m√y/n,整理得√y = n(m²/n² - x + y)/(2m).上式左边是无理数,右边是有理数,这一矛盾...