a-maths
回答 (1)
2007-07-04 5:34 am
✔ 最佳答案
2x² + 6x + 8= 2(x² + 3x + 4)
= 2[x² + 3x + (3/2)²] - 2(3/2)² + 8
= 2(x + 3/2)² + 7/2 > 0
So, f(x) = 1 / (2x² + 6x + 8) > 0 for all real values of x.
From the above, the minimum value of 2x² + 6x + 8 = 7/2 when x = -3/2
So, maximum value of f(x)
= 1 / (7/2)
= 2/7
參考: Myself~~~
收錄日期: 2021-04-23 20:36:37
原文連結 [永久失效]:
https://hk.answers.yahoo.com/question/index?qid=20070703000051KK04422