Question

(a+2b)*(a^2-2ab+4b^2)=
(a-b+c)*(a+b-c)=
(a+2b)*(a-2b)*(a^2+4b^2)=

Answer 1

$(a+2b)(a^2-2ab+4b^2)=a^3-8b^3\\(a-b+c)(a+b-c)=(a-(b-c))(a+(b-c))=a^2-(b-c)^2=\\=a^2-b^2+2bc-c^2\\(a+2b)(a-2b)(a^2+4b^2)=(a^2-4b^2)(a^2+4b^2)=a^4-16b^4$