a23456 发表于 23-10-2011 11:52
都是正整数
X+Y+Z=100
3X+2Y+0.5Z=100
Let Z = 2k X+Y=100-2k ...(1) 3X+2Y=100-k ...(2)
(2)-(1)x2, we have X = (100-k)-2(100-2k) = 3k - 100 From (1), Y = (100-2k)-(3k-100) = 200 - 5k
Thus, X=3k-100, Y=200-5k, Z=2k. Since X, Y and Z are positive integers. 100/3<K<200/5 33.3<K<40 K=34,35,36,37,38,39
All positive integers solutions are (X,Y,Z)=(2,30,68), (5,25,70), (8,20,72), (11,15,74), (14,10,76), (17,5,78) |