n2-n-90=0 n=?
回答 (1)
2015-06-08 5:06 am
✔ 最佳答案
n² - n - 90 = 0(n² - 10n) + (9n - 90) = 0
n(n-10) + 9(n-10) = 0
(n+9)(n-10) = 0
n + 9 = 0 or n - 10 = 0
n = -9 or n = 10
Answer: The value of n is -9 or 10.
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https://hk.answers.yahoo.com/question/index?qid=20150607000051KK00086