If the system of equations
$x+2y+3z=3$

$4x+3y-4z=4$ 
 $8x+4y-\lambda z=9+\mu$ 
Has infinitely many solutions, then the ordered pair $(\lambda ,\mu )$  is equal to 
 

$$\begin{gathered} x+2y+3z=3 \\ 4+3y-4z=4 \\ 8x+4y-\lambda z=9+\mu \end{gathered}$$

has infinitely solution  $(\lambda ,\mu )=$ $\Delta =\left|\begin{array}{ccc}1& 2& 3\\ 4& 3& -4\\ 8& 4& -\lambda \end{array}\right|=0\Rightarrow 5\lambda -72=0\Rightarrow \lambda =\frac{72}{5}$

${\Delta }_3=\left|\begin{array}{ccc}1& 2& 3\\ 4& 3& 4\\ 8& 4& 9+\mu \end{array}\right|=0\Rightarrow -5\mu -21=0\Rightarrow \mu =\frac{-21}{5}$