The sum of the products of elements of any row with the co-factors of corresponding elements is equal to Δ (Determinant).

Explanation:

If ,

then |A| = a₁₁C₁₁ + a₁₂C₁₂ + a₁₃C₁₃

= Sum of products of elements of R₁ with their corresponding cofactors

= Δ (Determinant)