Answer:
x³ + 8x² + 19x + 12
Explanation:
(x + 4)(x + 1)(x + 3) ← expand 2nd/ 3rd factors using FOIL
= (x + 4)(x² + 4x + 3)
Each term in the second factor is multiplied by each term in the first factor.
= x(x² + 4x + 3) + 4(x² + 4x + 3) ← distribute parenthesis
= x³ + 4x² + 3x + 4x² + 16x + 12 ← collect like terms
= x³ + 8x² + 19x + 12