Question

Разложи на множители $81- y^{20}$

Answer 1

$81-y^{20}=9^2-(y^{10})^2=(9-y^{10})(9+y^{10})=\\=(3^2-(y^5)^2)(9+y^{10})=(3-y^5)(3+y^5)(9+y^{10})$