Given: 4x + ky + 8 = 0 – eq 1

x + y + 1 = 0 – eq 2

Here,

a₁ = 4, b₁ = k, c₁ = 8

a₂ = 1, b₂ = 1, c₂ = 1

Given systems of equations has a unique solution

∴

≠

4 ≠ k

∴ k ≠ 4