數學題!!急急急急
回答 (2)
2007-08-10 9:32 pm
✔ 最佳答案
7^(x-1) - 7^x = 7^(x+1) - 557^(x-1) - 7^x - 7^(x+1) = -55
7^x(1/7 - 1 - 7) = -55
7^x = 7
x = 1
2007-08-10 9:36 pm
7^(x-1) - 7^x=7^(x+1) - 55
7^(x+1) + 7^x - 7^(x-1) = 55
(7^x)(7 + 1 - 7^-1) = 55
7^x = 55 / (7 + 1 - 7^-1)
7^x = 7^1
x = 1
7^(x+1) + 7^x - 7^(x-1) = 55
(7^x)(7 + 1 - 7^-1) = 55
7^x = 55 / (7 + 1 - 7^-1)
7^x = 7^1
x = 1
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原文連結 [永久失效]:
https://hk.answers.yahoo.com/question/index?qid=20070810000051KK02205