$a)\text{tak},st=7$

$b)y=\frac{x}{4}=\frac{1}{4}{x}^1,\text{tak},st=1$

$c)y=\frac{4}{x}=4x^{-1},\text{nie, poniewaz˙}-1\notin \mathbb{N}$

$d)y=6\sqrt{x}=6x^{\frac{1}{2}},\text{nie, poniewaz˙}\frac{1}{2}\notin \mathbb{N}$

$e)\text{tak},st=3$