Question 23

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Jambmaths question: 

if $\left| \begin{matrix}   5 & 3  \\   x & 2  \\\end{matrix} \right|=\left| \begin{matrix}   3 & 5  \\   4 & 5  \\\end{matrix} \right|$, find the value of x

Option A: 

34

Option B: 

4

Option C: 

5

Option D: 

7

Jamb Maths Solution: 

$\begin{align}  & Note:\text{ } \\ & \left| \begin{matrix}   a & b  \\   c & d  \\\end{matrix} \right|=ad-cb\text{      }\!\!\{\!\!\text{ Definition of determinant 2}\times \text{2 }\!\!\}\!\!\text{ } \\ & \left| \begin{matrix}   5 & 3  \\   x & 2  \\\end{matrix} \right|=\left| \begin{matrix}   3 & 5  \\   4 & 5  \\\end{matrix} \right| \\ & 10-3x=15-20 \\ & 10-3x=-5 \\ & -3x=-15 \\ & x=5 \\\end{align}$

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