The equation x^3+x^2+ax-4=0 has one root equal to - 2. Find the value of a.

a = - 4

Step-by-step 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