English Deutsch Français Italiano Español Português 繁體中文 Bahasa Indonesia Tiếng Việt ภาษาไทย
所有分類

f(x)=x^6+3x^5-3x^4-6x^3+11x^2+27x-19
求 f( (-1+√3)/2 )=?

2005-11-10 13:47:04 · 1 個解答 · 發問者 ? 3 in 科學 數學

我知道您很會寫Matlab程式,但這裡是希望用手算的,是國中或高中問題,他們看不懂Matlab。

2005-11-12 05:04:22 · update #1

1 個解答

f(x)=x6+3x5-3x4-6x3+11x2+27x-19,求 f( (-1+√3)/2 )=? 解:設 x = (-1+√3)/2 則將此方程式展開如下-   2x = -1 + √3  =>  2x + 1 = √3   (2x + 1)2 = (√3)2  =>  4x2 + 4x + 1 = 3   4x2 + 4x -2 = 0  =>  2x2 + 2x - 1 = 0  所以化簡 f(x) = (2x2 + 2x - 1)(1/2 x4 + x3 - 9/4 x2 - 1/4 x +           37/8) + 25/2 x - 115/8          = 0 + (25/2)[(-1+√3)/2] + 115/8          = (-25 + 25√3)/4 + 115/8          = (65 + 50√3))/8

2005-11-13 02:54:27 · answer #1 · answered by Frank 7 · 0 0

fedest.com, questions and answers