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標題:

求未知數2條 - 10點

發問:

求未知數2條 - 10點 請求以下的A、B、C: 第一題: 1A + 2B + 1C = 20 2A + 2B = 22 2A + 1B + 1C = 21 第二題: 2A + 2B = 30 1A + 2B + 1C = 26 2A + 1B + 1C = 33

最佳解答:

第一題: 1A + 2B + 1C = 20 2A + 2B = 22 2A + 1B + 1C = 21 -------------------------- 2A + 2B = 22 A + B = 22/2 A = 11-B 1A + 2B + 1C = 20 (11-B) + 2B + 1 C = 20 11 + 1B + 1C = 20 C = 20-11- 1B C = 9-1B 2A + 1B + 1C = 20 2 (11-B) + 1B + 1(9-1B) = 21 22 - 2B + 1B + 9 – 1B = 21 31 – 2B = 21 31 - 21 = 2B 10 / 2 = B B = 5 2A + 2B = 22 2A + 2(5) = 22 2A+ 10 = 22 2A = 22-10 A = 12 / 2 A = 6 1A + 2B + 1C = 20 1(6) + 2(5) + 1C = 20 6 + 10 + 1C = 20 C = 20-10-6 C = 4 A = 6, B = 5, C = 4 第二題: 2A + 2B = 30 1A + 2B + 1C = 26 2A + 1B + 1C = 33 2A + 2B = 30 2 (A+B) = 30 1A + 1B = 30/2 A = 15 – 1B 1A + 2B + 1C = 26 1(15-B) + 2B + 1C =26 15 – 1B + 2B + 1C = 26 15 + 1B + 1C = 26 1C = 26-15-1B 1C = 11-1B 2A + 1B + 1C = 33 2(15-1B) + 1B + 1(11-1B) = 33 30 – 2B + 1B + 11 – 1B = 33 41 – 2B = 33 41 – 33 = 2B 8 = 2B B = 4 2A + 2B = 30 2A +2 (4) = 30 2 A+ 8 = 30 2A = 30-8 A = 22 /2 A = 11 1A + 2B + 1C = 26 1(11) + 2(4) +1C = 26 11+8+1C=26 19 + 1C = 26 C = 26-19 C=7 A = 11, B = 4 , C = 7

其他解答:

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第一題::: A=6 B=5 C=4 第二題::: A=11 B=4 C=7
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