Answer:
(x - 3) is a factor of f(x)
Step-by-step explanation:
If (x - h) is a factor of f(x) then f(h) = 0 ← factor theorem
Thus if (x - 3) is a factor of f(x) then f(3) = 0
f(3) = - 5(3)³ + 16(3)² - 9 = - 135 + 144 - 9 - 0
Thus (x - 3) is a factor of f(x)