Answer:
a = - 4
Explanation:
Given x = - 2 is a root then f(- 2) = 0
f(x) = x³ + x² + ax - 4, thus
f(- 2) = (- 2)³ + (- 2)² - 2a - 4 = 0, that is
f(- 2) = - 8 + 4 - 2a - 4 = 0, thus
- 8 - 2a = 0 ( add 8 to both sides )
- 2a = 8 ( divide both sides by - 2 )
a = - 4