If x + 1 is a factor of x3 + 3x2 + kx + 4, find the value of k
-
A.
6 -
B.
-6 -
C.
8 -
D.
-8
Correct Answer: Option A
Explanation
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