$4 x+3 y-4 z=4$

$8 x+4 y-\lambda z=9+\mu \quad \ldots \ldots . \text { (iii) }$

$\text { (i) } \times 4-\text { (ii) } \Rightarrow 5 y+16 z=8 \ldots \ldots \text { (iv) }$

$\text { (ii) } \times 2-\text { (iii) } \Rightarrow 2 y+(\lambda-8) z=-1-\mu \ldots \ldots(v)$

$\text { (iv) } \times 2-\text { (iii) } \times 5 \Rightarrow(32-5(\lambda-8)) z=16-5(-1-\mu)$

$\text { For infinite solutions } \Rightarrow 72-5 \lambda=0 \Rightarrow \lambda=\frac{72}{5}$

$21+5 \mu=0 \Rightarrow \mu=\frac{-21}{5}$

$\Rightarrow(\lambda, \mu) \equiv\left(\frac{72}{5}, \frac{-21}{5}\right)$