中二數學一題

先用我果方法計先
(x+1)(x-1)(x^2-1)
=(x^2-1^2)(x^2-1)
=(x^2-1)^2
=(x^2)^2-2(x^2)(1)+1^2
=x^4-2x^2+1//
如果我既答案係岩,而你既答案同我唔一樣,咁計係得嫁,你只不過係計錯數----
(x+1)(x-1)(x^2-1)
=(X+1)(X-1)(X+1)(X-1)
=(X-1)^2(X+1)^2
=(X^2-2X+1)(X^2+2X+1)
=X^4-4X^2+1 <--------呢度錯左

(X^2-2X+1)(X^2+2X+1)
=X^4-2X^3+X^2+2X^3-4X^2+2X+X^2-2X+1
=X^4-2X^2+1//

rubbish
(x+1)(x-1)(x^2-1)

=(x^2-1^2)(x^2-1)
=(x^2-1)^2
=X^4-2X^2+1(ans)

(x+1)(x-1)=x^2-1
(x^2-1)(x^2-1)=x^4-2x^2+1 其中分別分三項 第一是 X^2 第二是 -1個X^2 再-1個X^2 =-2個X^2 第三: (-)(-)得正=+1

答案似乎不正確。
=(x^2-1) (x^2-1)
=x(x-1) x(x-1)
=x(x^2-2x+1)

咁樣如果5係捉得緊都ok架!!! 咁計就無錯囉!!!