只可看看的方法:
由(x + 4y)(x + y - 18)
= (x - 2y)² + 9(xy - 2x - 8y)≥0,
得x + y≥18,
等号成立当且仅当x = 12∧y = 6.
只可看看的方法:
由(x + 4y)(x + y - 18)
= (x - 2y)² + 9(xy - 2x - 8y)≥0,
得x + y≥18,
等号成立当且仅当x = 12∧y = 6.
转载于:https://www.cnblogs.com/inequality/p/3157075.html