當 x = (√3-1)/2. 為什麼 14x^4 - 13x^2 + 15x - 5 = 0 呢?
回答 (1)
2019-12-19 9:46 pm
✔ 最佳答案
x=(√3 -1)/2(2x+1)²=3
2x²+2x-1=0 ......🤓
4x⁴ =(1-2x)²
14x⁴ =7(1-2x)²/2=14x²-14x+7/2 ......🧐
則 (14x⁴ -13x²+15x-5)²⁰¹⁹
= (14x²-14x+7/2 - 13x²+15x-5)²⁰¹⁹ ...用了🧐
= (x²+x-3/2)²⁰¹⁹
= ((2x²+2x-3)/2)²⁰¹⁹
= (- 2/2)²⁰¹⁹ ...用了🤓
= - 1
收錄日期: 2021-04-11 23:06:11
原文連結 [永久失效]:
https://hk.answers.yahoo.com/question/index?qid=20191219115652AAZpmud