If (begin{vmatrix} 2 & -4 \ x & 9 end{vmatrix} = 58), find the value of x.
-
A.
10 -
B.
30 -
C.
14 -
D.
28
Correct Answer: Option A
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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