JAMB - Mathematics (2019 - No. 23)
If \(\begin{vmatrix} 2 & -4 \\ x & 9 \end{vmatrix} = 58\), find the value of x.
10
30
14
28
Explanation
\(\begin{vmatrix} 2 & -4 \\ x & 9 \end{vmatrix} = 58\)
\(\implies (2 \times 9) - (-4 \times x) = 58\)
\(18 + 4x = 58 \implies 4x = 58 - 18 = 40\)
\(x = 10\)
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