Answer:
5. a^3 + b^3 = (a+b)^3 - 3ab(a+b)
Step-by-step explanation:
(a+b)^3
= (a+b) (a+b) (a+b)
={(a+b) (a+b)} (a+b)
={a(a+b) + b(a+b)} (a+b)
=(a^2 + ab + ab + b^2) (a+b)
=(a^2 + b^2 + 2ab) (a+b)
=a^2(a+b) + b^2(a+b) + 2ab(a+b)
=a^3 + a^2b + ab^2 + b^3 + 2a^2b + 2ab^2
=a^3 + b^3 + 3a^2b + 3ab^2
=a^3 + b^3 + 3ab(a+b)
(a+b)^3 = a^3 + b^3 + 3ab(a+b)
(a+b)^3 - 3ab(a+b) = a^3 + b^3
a^3 + b^3 = (a+b)^3 - 3ab(a+b)
Hope this helped!
