Answer
$$a^3 - b^3$$
Work Step by Step
To multiply a binomial with a trinomial, you want to multiply each term of the binomial with each of the terms in the trinomial:
$$a(a^2) + a(ab) + a(b^2) - b(a^2) - b(ab) - b(b^2)$$
We multiply the terms to simplify:
$$a^3 + a^2b + ab^2 - a^2b - ab^2 - b^3$$
Now group like terms together:
$$a^3 + (a^2b - a^2b) + (ab^2 - ab^2) - b^3$$
We combine like terms:
$$a^3 - b^3$$
