The given expression, x^2 + 8x + 15, can be factored as (x + 5)(x + 3). This is because when we multiply these factors, we get x^2 + 8x + 15. The first term of each factor, x, multiplied together gives x^2. The outer terms, x and 3, when multiplied give 3x. The inner terms, 5 and x, when multiplied give 5x. Finally, the last terms, 5 and 3, when multiplied give 15. Adding all these terms together gives us the original expression. Therefore, (x + 5)(x + 3) is the correct factorization.