Question

已知x的2次方＋x－1＝0，试求x的3次方＋2x的2次方＋2013的值

Answer 1

x^2 - x - 1 = 0 x^2 = x + 1 -x^3 + 2x^2 +2013 = (-x^3 + x^2) + x^2 + 2013= -x^2(x - 1) + x^2 + 2013= -(x + 1)(x - 1) + x^2 + 2013= -x^2 + 1 + x^2 + 2013= 2014