Answer:
x³ + 9x² + 23x + 15
Step-by-step explanation:
Given
(x + 1)(x + 3)(x + 5) ← expand the first pair of factors using FOIL
= (x² + 4x + 3)(x + 5)
Each of the terms in the second factor is multiplied by each of the terms in the first factor, that is
x²(x + 5) + 4x(x + 5) + 3(x + 5) ← distribute the 3 parenthesis
= x³ + 5x² + 4x² + 20x + 3x + 15 ← collect like terms
= x³ + 9x² + 23x + 15 ← in the form ax³ + bx² + cx + d
