因為 2x² - 2x - 1 = 0 且 2y² - 2y - 1 = 0
所以當 x = y 時,y/x + x/y = 1 + 1 = 2
當 x ≠ y 時,x 和 y 是方程 2t² - 2t - 1 = 0
根據(jù)韋達定理,得：
x + y = 1,xy = -1/2
所以
y/x + x/y
= (x² + y²)/xy
= [(x + y)² - 2xy]/xy
= (x + y)²/xy - 2
= 1/(-1/2) - 2
= -2 - 2
= -4
綜上 y/x + x/y = 2 或 -4