x²+x=1 所以x^4+2x³-x²-2x =(x^4-x²)+(2x³-2x) =x²(x²-1)+2x(x²-1) =x²(x+1)(x-1)+2x(x+1)(x-1) =(x²+x)[x(x-1)+2(x-1)] =x²-x+2x-2 =x²+x-2 =1-2 =-1 所以原式=2004
