Combining like terms, we have:
(3x + 9) + (-x² - 15x - 40)= 3x + 9 - x² - 15x - 40= -x² - 12x - 31
So, (3x + 9) + (-x² - 15x - 40) = -x² - 12x - 31
Combining like terms, we have:
(3x + 9) + (-x² - 15x - 40)
= 3x + 9 - x² - 15x - 40
= -x² - 12x - 31
So, (3x + 9) + (-x² - 15x - 40) = -x² - 12x - 31