由x^2+x+1=0两边乘以x-1得：x^3=1故：x^4+3x^3+5x^2+4x+1997=x+3+5x^2+4x+1997=5x^2+5x+2000=5(x^2+x+1)+1995=1995x^4+1/x^4=(x²+1/x²)²-2=[(x+1/x)²-2]²-2由x^2-13x+1=0知x≠0两边除以x得...