(a-1)(a+1)(a²+1)(a⁴+1)

Question

(a-1)(a+1)(a²+1)(a⁴+1)

Answer 1

(a-1)(a+1)(a²+1)(a⁴+1)=[(a-1)(a+1)](a²+1)(a⁴+1)=
=[(a²-1)(a²+1)](a⁴+1)=((a²)²-1)(a⁴+1)=(a⁴-1)(a⁴+1)=
=((a⁴)²-1)(a⁴+1)=a⁸-1