$a)$

$f\left(-5\right)=1$

$f\left(0\right)=4$

$f\left(4\right)=-2$

$f\left(6\right)=2$

$f_{min}=-2dlax=4$

$f_{\max }=5dlax=2$

 

 

$b)$

$f\left(-5\right)=4$

$f\left(0\right)=0$

$f\left(4\right)=5$

$f\left(6\right)=3$

$f_{min}=0dlax=0$

$f_{\max }=5dlax=4$