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WAEC Further Mathematics 2018 Paper

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Question : 21

Total: 40

If the determinant of the matrix

\begin{pmatrix} 2 & x \\ 3 & 5 \end{pmatrix}=13

, find the value of

x

.

-2
-1
1
2

Solution:

Concept:

For a

2 \times 2

matrix

\begin{pmatrix} a & b \\ c & d \end{pmatrix}

, the determinant is

ad - bc

.

Explanation:

Here, the matrix is

\begin{pmatrix} 2 & x \\ 3 & 5 \end{pmatrix}

. So

a = 2

,

b = x

,

c = 3

, and

d = 5

.

Using the determinant formula:

2 \cdot 5 - 3 \cdot x = 10 - 3x

.

Given:

10 - 3x = 13

.

Subtract

10

from both sides:

-3x = 3

.

Divide both sides by

-3

:

x = -1

.

Answer:

x = -1

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