1.

For which of the following element in the determinant Δ=\(\begin{vmatrix}5&-5&8\\6&2&-1\\5&-6&8\end{vmatrix}\) , the minor and the cofactor both are zero.(a) -5(b) 2(c) -6(d) 8The question was posed to me in an online interview.The doubt is from Determinants topic in division Determinants of Mathematics – Class 12

Answer» RIGHT answer is (b) 2

For explanation: Consider the element 2 in the determinant Δ=\(\begin{vmatrix}5&-5&8\\6&2&-1\\5&-6&8\end{vmatrix}\)

The minor of the element 2 is given by

∴M22=\(\begin{vmatrix}5&8\\5&8\end{vmatrix}\)=40-40=0

⇒A22=(-1)^2+2 (0)=0.


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