Answer:
10x³ + 28x² - 12x - 18
Explanation:
Given
(5x² - x - 3)(2x + 6)
Each term in the second factor is multiplied by each term in the first factor, that is
5x²(2x + 6) - x(2x + 6) - 3(2x + 6) ← distribute the parenthesis
= 10x³ + 30x² - 2x² - 6x - 6x - 18 ← collect like terms
= 10x³ + 28x² - 12x - 18