Expanding the right hand side and separating terms on the left hand side gives ( λ λ 1 + A T ) ⋅ ⋅ [ ∂ ∂ I 1 ∂ ∂ A λ λ 2 + ∂ ∂ I 2 ∂ ∂ A λ λ + ∂ ∂ I 3 ∂ ∂ A ] = [ λ λ 3 + I 1 λ λ 2 + I 2 λ λ + I 3 ] 1