Question

Find the value of x, if \(\begin{vmatrix}2&5\\3&x\end{vmatrix}\)=\(\begin{vmatrix}x&-1\\5&3\end{vmatrix}\).

(a) 20

(b) -20

(c) 30

(d) -30

This question was addressed to me during an online exam.

Question is taken from Determinant topic in portion Determinants of Mathematics – Class 12

Answer 1

The correct choice is (b) -20

The explanation: \(\begin{vmatrix}2&5\\3&x\end{vmatrix}\)=\(\begin{vmatrix}x&-1\\5&3\end{vmatrix}\)

⇒2x-15=3x+5

⇒x=-20