已知x=1/（2－√5）,求x＋3x－5x＋1的值
问题描述：
已知x=1/（2－√5）,求x＋3x－5x＋1的值
答
x=1/(2-√5) x=(2+√5)/(2-√5)(2+√5) x=-2-√5 x^3+3x^2-5x+1 =x^3+3x^2-4x-x+1 =x(x^2+3x-4)-(x-1) =x(x-1)(x+4)-(x-1) =(x-1)(x^2+4x-1) =(x-1)(x^2+4x+4-5) =(x-1)[(x+2)^2-5] =(x-1)[(-2-√5+2)^2-5] =(x-1)[(...