Jambmaths question:
If $2{{x}^{2}}-kx-12$is divisible by $x-4$, find the value of k
Option A:
4
Option B:
5
Option C:
6
Option D:
7
Jamb Maths Solution:
$\begin{align} & \text{let }f(x)=(2{{x}^{2}}-kx-12) \\ & \text{since (}x-4)\text{ is factor of }f(x),\text{then} \\ & \text{ }f(4)=0 \\ & f(4)=2{{(4)}^{2}}-k(4)-12=0 \\ & 32-4k-12=0 \\ & k=5 \\\end{align}$
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