Re: [中學] 聯立方程
※ 引述《KAINTS (RUKAWA)》之銘言:
: |150m-k|=50
: |240n-k|=20
: 其中m,n為整數,且k<1000
: m,n=???
: 有沒有什麼方法解比較快??
k = 150m ±50
=> 20 = |240n-k| = |240n-150m±50|
=> ±2 = 24n-15m±5
=> 24n-15m = ±7 (無解)or ±3
=> 8n-5m = ±1
=> Case I:8n-5m=1
=> (m,n)=(3,2),(-5,-3),...,(-5-8a,-3-5a),...
Case II:8n-5m=-1
=> (m,n)=(5,3),...,(5-8a,3-5a),...
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11/17 20:37, , 1F
11/17 20:37, 1F
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