解方程~~[請進]急..幫手!!!
2012-09-24 1:23 am
回答 (2)
2012-09-24 1:45 am
✔ 最佳答案
8.x² + 10x + 21 = 0
(x + 3)(x + 7) = 0
x = -3 or x = -7
10.
x² - 17x + 60 = 0
(x - 5)(x - 12) = 0
x = 5 or x = 12
12.
x² - 7x - 30 = 0
(x + 3)(x - 10) = 0
x = -3 or x = 10
14.
x² - 2x - 15 = 0
(x + 3)(x - 5) = 0
x = -3 or x = 5
參考: sioieng
2012-09-24 1:38 am
Hint: factorize them.
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原文連結 [永久失效]:
https://hk.answers.yahoo.com/question/index?qid=20120923000051KK00473