x²-x+1=（x²+x+1）（x²+2x+4） (x²+x+1)(x²+2x+4)-(x²-x+1)=0 (x²+x+1)(x²+2x+1+3)-(x²-x+1)=0 (x²+x+1)(x²+2x+1)+3(x².