Co-factors of first column of determinant \(\begin{vmatrix}5&20\\[0.3em]3&-1\end{vmatrix}\)

Question

Co-factors of first column of determinan

\(\begin{vmatrix}5&20\\[0.3em]3&-1\end{vmatrix}\)

(a) -1, 3

(b) -1,- 3

(c)- 1, 20

(d) – 1,- 20

Answer 1

Answer is (d)

\(\begin{vmatrix}5&20\\[0.3em]3&-1\end{vmatrix}\)

Co-factor of a₁₁

F₁₁ = (- 1)² M₁₁

= 1 x (- 1) = – 1

Co-factor of a₁₂

F₂₁ = (-1)¹¹ M₂₁

= (- 1) × 20 = – 20