已知x^2+x-1=0,求2002x^3+2001x^2-2003x-2004的值

已知x^2+x-1=0,求2002x^3+2001x^2-2003x-2004的值

2002x^3+2001x^2-2003x-2004
=x(2002x²+2001x-2003)-2004
=x(2001x²+2001x-2001+x²-2)-2004
=x(x²-2)-2004
=x(1-x-2)-2004
=-x²-x-2004
=-1-2004
=-2005

因式分解:X的三次方-X的平方-X+1

=x(X的平方-1)-(X的平方-1)
=(x-1)(x-1)(x+1)