Skip to main contentSkip to solution

Let ∣x218x∣=∣−4−2−8−4∣\begin{vmatrix} x & 2 \\ 18 & x \end{vmatrix} = \begin{vmatrix} -4 & -2 \\ -8 & -4 \end{vmatrix}. Then

(A) x=−4x = -4

(B) x=−6x = -6

(C) x=4x = 4

(D) x=6x = 6

Choose the correct answer from the options given below:

Solution

✅ Correct Option: 4

For a 2×2 matrix ∣abcd∣\begin{vmatrix} a & b \\ c & d \end{vmatrix}, the determinant is calculated as:

ad−bcad - bc


For the left side: ∣x218x∣\begin{vmatrix} x & 2 \\ 18 & x \end{vmatrix}

=x×x−2×18= x \times x - 2 \times 18

=x2−36= x^2 - 36


For the right side: ∣−4−2−8−4∣\begin{vmatrix} -4 & -2 \\ -8 & -4 \end{vmatrix}

=(−4)×(−4)−(−2)×(−8)= (-4) \times (-4) - (-2) \times (-8)

=16−16= 16 - 16

=0= 0


The equation becomes:

x2−36=0x^2 - 36 = 0

x2=36x^2 = 36

x=±6x = \pm 6

Therefore, x=6x = 6 or x=−6x = -6


Both options (B) x=−6x = -6 and (D) x=6x = 6 are correct.

The answer is (B) and (D).

Keyboard Shortcuts

  • Left arrow: Previous question
  • Right arrow: Next question
  • S key: Jump to solution
  • Q key: Jump to question