Question

ay^7 + y^7 - ay^3 - y^3​

Answer 1

$ay^7+y^7-ay^3-y^3=(a+1)y^7-y^3(a+1)=\\=(a+1)(y^7-y^3)=(a+1)cdot y^3, (y^4-1)=\\=y^3cdot (a+1)(y^2-1)(y^2+1)=y^3cdot (a+1)cdot (y-1)cdot (y+1)cdot (y^2+1)$