a(a^2-1)—a^2+1=a(a²-1)-(a²-1)=(a²-1)(a-1)=(a-1)(a+1)(a-1)=(a-1)²(a+1)
a(a²-1)-a²+1=a(a²-1)-(a²-1)=(a²-1)(a-1)=(a+1)(a-1)(a-1)
a(a^2-1)—a^2+1=a^3-a^2-a+1=a^2(a-1)-(a-1)=(a-1)(a^2-1)=(a+1)*(a-1)^2
