回覆 35# satsuki931000 的帖子
第 14 題
w = a,z = a + b,y = a + b + c,x = a + b + c + d,其中 a、b、c、d ≧ 0
5x + 4y + 3z + 6w = 18a + 12b + 9c + 5d = 2013
x + y + z + w = 4a + 3b + 2c + d
4(4a + 3b + 2c + d) = 18a + 12b + 9c + 5d - (2a + c + d) ≦ 2013
x + y + z + w = 4a + 3b + 2c + d ≦ 2013 / 4
等號成立於 a = c = d = 0,即 x = y = z = 2013 / 12,w = 0
5(4a + 3b + 2c + d) = 18a + 12b + 9c + 5d + (2a + 3b + c) ≧ 2013
x + y + z + w = 4a + 3b + 2c + d ≧ 2013 / 5
等號成立於 a = b = c = 0,即 x = 2013 / 5,y = z = w = 0