Let \( \alpha , \beta \in \mathbb{R} \) be such that the system of linear equations\( x + 2y + z = 5 \)\( 2x + y + \alpha z = 5 \)\( 8x + 4y + \beta z = 18 \)has no solution. Then \( \dfrac{\beta}{\alpha} \) is equal to:
\( -4 \)
\( 4 \)
\( 8 \)
\( -8 \)