If \(\begin{vmatrix} 2 & -4 \\ x & 9 \end{vmatrix} = 58\), find the value of x.

  • A 10
  • B 30
  • C 14
  • D 28
jamb 2019mathematics

The correct answer is A. 10

The determinant of a 2x2 matrix \(\begin{vmatrix} a & b \\ c & d \end{vmatrix}\) is given by \(ad - bc\). In this case, we have \(2 \times 9 - (-4) \times x = 58\).

Simplifying, we get \(18 + 4x = 58\), then \(4x = 58 - 18 = 40\), and finally \(x = \frac{40}{4} = 10\).

Previous question Next question