If begin vmatrix 2 amp -4 x amp 9 end vmatrix 5... - JAMB Mathematics 2019 Question
If \(\begin{vmatrix} 2 & -4 \ x & 9 \end{vmatrix} = 58\), find the value of x.
A
10
B
30
C
14
D
28
correct option: a
\(\begin{vmatrix} 2 & -4 \ x & 9 \end{vmatrix} = 58\)
\(\implies (2 \times 9) - (-4 \times x) = 58\)
\(18 + 4x = 58 \implies 4x = 58 - 18 = 40\)
\(x = 10\)
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