Answer:
c = - 2
Step-by-step explanation:
Since (z - 3) is a factor of p(z) then z = 3 is a root and p(3) = 0
p(3) = 3³ + 9c - 4(3) + 3 = 0, hence
27 + 9c - 12 + 3 = 0 ⇒ 9c = - 18 ⇒ c = - 2
