Question

Mark (✓) against the correct answer in each of the following:
The value of k, for which the polynomial x³ − 4x² + 2x + k has 3 as its zero, is
(a) 3
(b) −3
(c) 6
(d) −6

Answer 1

(a) 3

Let f(x) = x³ − 4x² + 2x + k.
3 is the zero of f(x).
Therefore, f(3) = 0
$$\begin{gathered} \Rightarrow 3^3-4\times 3^2+2\times 3+k=0 \\ \Rightarrow 27-36+6+k=0 \\ \Rightarrow -3+k=0 \\ \therefore k=3 \end{gathered}$$