(x^3 - x + x^3 - 1)如何转化成(x-1)(2x^2+x^2+1)?

题目

(x^3 - x + x^3 - 1)如何转化成(x-1)(2x^2+x^2+1)?
计算差,卡在这了,拜托写的详细点`
(x^3 - x + x^3 - 1)如何转化成(x-1)(2x^2+x^2+1)
那里不对呢？

答案

x³-x+x³-1
=x(x²-1)+(x-1)(x²+x+1)
=x(x+1)(x-1)+(x-1)(x²+x+1)
=(x-1)(x²+x+x²+x+1)
=(x-1)(2x²+2x+1)