Question -
Answer -
The given determinant is
.
We have:
M21 = 
∴A21 = cofactor of a21 =(−1)2+1 M21 = 7
M22 = 
∴A22 = cofactor of a22 =(−1)2+2 M22 = 7
M23 =
∴A23 = cofactor of a23 =(−1)2+3 M23 = −7
We know that Δ is equal to the sum of theproduct of the elements of the second row with their corresponding cofactors.
∴Δ = a21A21 + a22A22 + a23A23 =2(7) + 0(7) + 1(−7) = 14 − 7 = 7