Maths--Inequalities & Identities
2008-11-23 3:14 am
Given that (A+B)²=A²+2AB+B². Prove that 9x²-6x+2 is a positive number for any rational number x.
回答 (4)
2008-11-23 3:45 am
✔ 最佳答案
9x^2 - 6x + 2= (3x)^2 - 2(3x) + 2
= (3x)^2 - 2(3x) + 1 + 1
=[3x - 1]^2 + 1.
since [3x -1]^2 is always postive, [3x-1]^2 + 1 = 9x^2 - 6x + 2 is always postive.
2008-11-24 6:42 am
唔該晒你地既提醒！
2008-11-23 8:46 am
(3x-1)^2 is always non-negative
2008-11-23 7:13 am
當[3x -1]^2等於0果陣並唔係positive
所以應該話[3x -1]^2>=0
所以應該話[3x -1]^2>=0
收錄日期: 2021-04-25 22:35:54
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