If the acute angle between the lines $3x-y+1=0$ , $2x+ky+5=0$  is $45°$ , then the value of $\text{'}k\text{'}$  is

$\tan \theta =\left|\frac{a_1{b}_2-a_2{b}_1}{a_1{a}_2+b_1{b}_2}\right|$

$\tan 45°=\left|\frac{3k+2}{6-k}\right|\Rightarrow \frac{3k+2}{6-k}=\pm 1$

$\Rightarrow 3k+2=1\left(6-k\right)$

$\Rightarrow k=1$

$\Rightarrow 3k+2=-1\left(6-k\right)$

$\Rightarrow k=-4$ .