Question

Find the co-factors of the elements a₁₁ and a₂₁ of matrix A = `[(1, 2),(3, 4)]`.

Answer 1

Given: A = `[(1, 2),(3, 4)]`

Here, a₁₁ = 1, M₁₁ = 4

∴ A₁₁ = (−1)¹⁺¹ M₁₁ = 1(4) = 4

Also, a₂₁ = 3, M₂₁ = 2

∴ A₂₁ = (−1)²⁺¹ M₂₁ = (−1)(2) = −2

Hence, co-factors of a₁₁ and a₂₁ are 4 and −2, respectively.