Answer:
x^3 + 4x^2 - 9.
Step-by-step explanation:
(x + 3)(x^2 + x - 3)
= x(x^2 + x - 3) + 3(x^2 + x - 3)
= x^3 + x^2 - 3x + 3x^2 + 3x - 9
= x^3 + 4x^2 - 9.
