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Question:

If the adjoint of a 3x3 matrix P is ⎡⎢⎣144217113⎤⎥⎦, then the possible value(s) of the determinant of P is (are):

𕒶

1

𕒵

2

Solution:

Adj.P = ∣∣∣∣144217113∣∣∣∣
Let A be a square matrix of order n. Then, we know that
Adj(A) = |A| * A⁻¹
Also, A * Adj(A) = Adj(A) * A = |A|I
where I is the identity matrix of order n.
Given that Adj(P) = ∣∣∣∣144217113∣∣∣∣
|Adj(P)| = 1(7-7)-4(2-7)+4(2-7) = 0
We know that for a 3x3 matrix P, |Adj(P)| = |P|²
Therefore, |P|² = 0
This implies that |P| = 0