For Δ = det[2, -3, 1; 5, 4, -2; 1, 6, 3], what is the cofactor A₁₂?

Determinants, Adjoint & Inverse · Question 39 of 87

Question 39

MediumOriginal question

For $\Delta = \begin{vmatrix}2 & -3 & 1 \\ 5 & 4 & -2 \\ 1 & 6 & 3\end{vmatrix}$ , what is the cofactor $A_{12}$ ?

-20

Correct answerYour answer

-17

Correct answerYour answer

-15

Correct answerYour answer

17

Correct answerYour answer

Show the answer and explanation

CorrectNot quiteAnswer B

Correct answer: B

Delete row 1 and column 2: $M_{12} = \begin{vmatrix}5 & -2 \\ 1 & 3\end{vmatrix} = 17$ .
The cofactor is $A_{12} = (-1)^{3}M_{12} = -17$ .

Worth noting

$17$ is the minor; the place $(1, 2)$ has the sign $-1$ .

Ten questions from Determinants, Adjoint & Inverse, at your own pace.

Ten questions from Determinants, Adjoint & Inverse, at your own pace.