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
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⤋