Answer:
see explanation
Step-by-step explanation:
(f - g)(x) = f(x) - g(x) , that is
f(x) - g(x)
= - 5x³ - 4x² + 8x - (- 4x² + 8) ← distribute parenthesis by - 1
= - 5x³ - 4x² + 8x + 4x² - 8 ← collect like terms
= - 5x³ + 8x - 8
Substitute x = - 2 into this expression, thus
(f - g)(- 2)
= - 5(- 2)³ + 8(- 2) - 8
= - 5(- 8) - 16 - 8
= 40 - 16 - 8
= 16
