$\text{a)}$  

$f\left(x\right)=-1\text{dla}x\in \left\{-4,0\right\}$  

$f\left(x\right)=3\text{dla}x=2$  

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$\text{b)}$  

$g\left(x\right)=0\text{dla}x=0$  

$g\left(x\right)=2\text{dla}x\in \left\{-1,1\right\}$  

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$\text{c)}$  

$h\left(x\right)=-2\text{dla}x=-3$  

$h\left(x\right)=1\text{dla}x\in ⟨2,4)$