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Ex 4.3, 3 - Chapter 4 Class 12 Determinants
Last updated at August 13, 2026 by Teachoo
Evaluating determinant using minor and co-factor
Chapter 4 Class 12 Determinants
Concept wise
- Finding determinant of a 2x2 matrix
- Evalute determinant of a 3x3 matrix
- Area of triangle
- Equation of line using determinant
- Finding Minors and cofactors
-
Evaluating determinant using minor and co-factor
- Find adjoint of a matrix
- Finding Inverse of a matrix
- Inverse of two matrices and verifying properties
- Finding inverse when Equation of matrice given
- Checking consistency of equations
- Find solution of equations- Equations given
- Find solution of equations- Statement given
- Verifying properties of a determinant
- Two rows or columns same
- Whole row/column zero
- Whole row/column one
- Making whole row/column one and simplifying
- Proving Determinant 1 = Determinant 2
- Solving by simplifying det.
- Using Property 5 (Determinant as sum of two or more determinants)
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Transcript
Ex 4.3, 3 Using Cofactors of elements of second row, evaluate ∆ = |■8(5&3&8@2&0&1@1&2&3)| Δ = a21 A21 + a22 A22 + a23 A23 a21 = 2, a21 = 0, a21 = 1, Calculating cofactor of second row i.e. A21 , A22 , And A23 M21 = |■8(5&3&8@2&0&1@1&2&3)|= |■8(3&8@2&3)| = 3 × 3 – 2 × 8 = 9 – 16 = –7 M22 = |■8(5&3&8@2&0&1@1&2&3)| = |■8(5&8@1&3)| = 5 × 3 – 8 × 1= 15 – 8 = 7 M23 = |■8(5&3&8@2&0&1@1&2&3)| = |■8(5&3@1&2)| = 5 × 2 –1 × 3 = 10 – 3 = 7 Cofactor of a21 = A21 = (–1)2 + 1 M21 = (–1)3 × –7 = –1 × –7 = 7 Cofactor of a22 = A22 = (–1)2 + 2 M22 = (–1)4 . 7 = 7 Cofactor of a23 = A23 = (−1)2 + 3 M31 = (–1)5 . (7) = (–1) (7) = –7 Now Δ = a21 A21 + a22 A22 + a23 A23 = 2 × 7 + 0 × 7 + 1 × (−7) = 14 + 0 − 7 = 7
