Answer:
5x² - 10x - 15
Explanation:
Given
(5x + 5)(x - 3)
Each term in the second factor is multiplied by each term in the first factor, that is
5x(x - 3) + 5(x - 3) ← distribute both parenthesis
= 5x² - 15x + 5x - 15 ← collect like terms
= 5x² - 10x - 15