Practicing Success

Target Exam

CUET

Subject

-- Mathematics - Section B1

Chapter

Matrices

Question:

If the adjoint of a 3 × 3 matrix P is $\begin{bmatrix}1&4&4\\2&1&7\\1&1&3\end{bmatrix}$ the possible values of the determinant of P are

Options:

± 2

± 1

± 3

± 4

Correct Answer:

± 2

Explanation:

If A is an $n × n$ matrix, then $|adj\, A| = |A|^{n-1}$

$∴\begin{vmatrix}1&4&4\\2&1&7\\1&1&3\end{vmatrix}=|P|^2$

$⇒|P|^2=1(3-7)-4 (6-7)+4(2-1)=4$

$⇒|P|^2=± 2$