First slide

Applications of determinant

Question

$If the matrix [\begin{array}{ccc} 1 & - 1 & 2 \\ 3 & 2 & 1 \\ - 1 & α & 3 \end{array}] is singular then α =$

Easy

A

2
B

-2
C

4
D

-4

Solution

$\begin{array}{l} \Rightarrow 6 - α + 1 (9 + 1) + 2 (3 α + 2) = 0 \\ \Rightarrow 6 - α + 10 + 6 α + 4 = 0 \\ \Rightarrow 5 α + 20 = 0 \\ \Rightarrow α = - 4 \end{array}$

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