If x + 1 is a factor of x3 + 3x2 + kx + 4, find the value of k
A
6
B
-6
C
8
D
-8
Verified Correct Answer: A.
Step-by-Step Mathematical Solution
x + 1 is a factor of x3 + 3x2 + kx + 4
Let f(x) = x3 + 3x2 + kx + 4
∴ f(-1) = (-1)3 + 3(-1)2 + k(-1) + 4 = 0
-1 + 3 - k + 4 = 0
∴ k = 6
Source: Myschool Past Questions Archive (Record #31316)