8 6 a - a
a^8 - a^6
1*(a + 1)*(a + 0)*(a - 1)
((1*(a + 1))*(a + 0))*(a - 1)
6 a *(1 + a)*(-1 + a)
a^6*(1 + a)*(-1 + a)
6 / 2\ a *\-1 + a /
a^6*(-1 + a^2)