a3 + b3 + c3 - 3abc= ( a + b + c ) ( a2 + b2 + c2-ab - bc - ac ). Prove both quations. Plzdo it quick :V.
(a+b+c)(a2+b2+c2-ab-bc-ca)
= a^3+ab^2+ac^2-a^2b-abc-ca^2 + ba^2+b^3+bc^2-ab^2-b^2c-bca + ca^2+cb^2+c^3-cab-bc^2-c^2a
= (a^3+b^3+c^3) + (ab^2-ab^2) + (ac^2-c^2a) + (-a^2b+ba^2) + (-abc-bca-cab) + (-ca^2+ca^2) + (bc^2-bc^2) + (-b^2c+c^2b)
= a^3+b^3+c^3 -3abc
= a^3+ab^2+ac^2-a^2b-abc-ca^2 + ba^2+b^3+bc^2-ab^2-b^2c-bca + ca^2+cb^2+c^3-cab-bc^2-c^2a
= (a^3+b^3+c^3) + (ab^2-ab^2) + (ac^2-c^2a) + (-a^2b+ba^2) + (-abc-bca-cab) + (-ca^2+ca^2) + (bc^2-bc^2) + (-b^2c+c^2b)
= a^3+b^3+c^3 -3abc