[理工] [離散] 97台科資工
Please determine the number of integer solutions for soliving
x1+x2+x3+x4 < 15, x1,x2,x3,x4 > 0
我看到解答這樣寫:
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令x5 = 15-(x1+x2+x3+x4)
=> x1+x2+x3+x4+x5 = 15, x1,x2,x3,x4,x5 > 0
令yi = xi-1, i = 1,2,3,4,5
=> y1+y2+y3+y4+y5 = 10, yi ≧ 0, i = 1,2,3,4,5
=> 整數解個數為 H(5,10) = C(14,10)
______
我想要知道
為什麼黃色那段會變成 x1+x2+x3+x4+x5 = 15 ??
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02/27 21:29, , 1F
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02/27 21:32, 3F
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02/27 21:33, , 4F
02/27 21:33, 4F
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02/27 21:36, , 5F
02/27 21:36, 5F
不過我傻傻的一開始就寫下了
x1+x2+...+x12 <= 72, 1<=xi<=6 ......虐待自己幹嘛?
※ 編輯: annheilong 來自: 61.228.128.151 (02/27 21:37)