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两條A-maths問題
2011-05-29 2:02 am
回答 (1)
2011-05-29 2:35 am
✔ 最佳答案
1) Sub u = x3 + 9x, then du = (3x2 + 9)dx, i.e. du/3 = (x2 + 3)dx∫ (x2 + 3)dx/(x3 + 9x)2 = (1/3) ∫ du/u2
= - 1/(3u) + C
= -1/[3(x3 + 9x)] + C
2) (m - 2)(m + 2) = m + 26
m2 - 4 = m + 26
m2 - m - 30 = 0
(m - 6)(m + 5) = 0
m = 6 or -5 (rej. since m is even)
So the nos. are 4, 6 and 8
參考: 原創答3
收錄日期: 2021-04-26 13:21:57
原文連結 [永久失效]:
https://hk.answers.yahoo.com/question/index?qid=20110528000051KK00913