(x^2-x+1)(x^2+x-1)
=(x^2-(x-1))(x^2+x-1)
=x^4-(x-1)²
=x^4-x²+2x-1
(x^2-x+1)(x^2+x-1)
=[x^2-(x-1)](x^2+x-1)
=x^4-(x-1)²
=x^4-(x²-2x+1)
=x^4-x²+2x-1
(x^2-x+1)(x^2+x-1)=[x^2-(x-1)](x^2+x-1)=x^4-(x-1)^2
=x^4-x^2+2x-1
(x^2-x+1)(x^2+x-1)
=x^4-(x-1)^2
=x^4-x^2+2x-1
(x^2-x+1)(x^2+x-1)=[x^2-(x-1)][x^2+(x-1)]=(x^2)^2-(x-1)^2=x^4-(x^2-2x+1)=x^4-x^2+2x-1
。。。。写成[x^2-(x-1)][x^2+(x-1)]
平方差公式,得x^4-(x-1)^2=x^4-x^2+2x-1