Question:medium

If $\begin{vmatrix}2x& 5 \\ 8 & x\end{vmatrix}=\begin{vmatrix}6 &-2 \\ 7& 3\end{vmatrix}$ then the value of $x$ is

Show Hint

Unlike matrices, determinants are values. Expand both sides fully before trying to isolate the variable.
  • 3
  • $\pm 6$
  • -3
  • +2
Show Solution

The Correct Option is B

Solution and Explanation

To solve the given equation, we need to evaluate and compare the determinants on both sides:

Given:

\(\begin{vmatrix}2x & 5 \\ 8 & x\end{vmatrix} = \begin{vmatrix}6 & -2 \\ 7 & 3\end{vmatrix}\)

The determinant of a 2x2 matrix \(\begin{vmatrix}a & b \\ c & d\end{vmatrix}\) is calculated as \(ad-bc\).

Let's calculate the determinant on the left side:

\(\begin{vmatrix}2x & 5 \\ 8 & x\end{vmatrix} = (2x)(x) - (5)(8)\)

\(= 2x^2 - 40\)

Now, let's calculate the determinant on the right side:

\(\begin{vmatrix}6 & -2 \\ 7 & 3\end{vmatrix} = (6)(3) - (-2)(7)\)

\(= 18 + 14\)

\(= 32\)

Equating the determinants:

\(2x^2 - 40 = 32\)

Solving for \(x\), we get:

\(2x^2 = 72\)

\(x^2 = 36\)

Taking the square root on both sides, we find:

\(x = \pm 6\)

Thus, the values of \(x\) that satisfy the equation are \(\pm 6\). Hence, the correct answer is \(\pm 6\).

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