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a)
$D\left(\frac{2}{2x+4}\right)=$
$f\left(x\right)=2{,}\ f'\left(x\right)=0\ ja\ g\left(x\right)=2x+4{,}\ g'\left(x\right)=2$
$\frac{0\left(2x+4\right)-2\cdot2}{\left(2x+4\right)^2}=-\frac{4}{\left(2x+4\right)^2}=-\frac{1}{\left(x+1\right)^2}$
b)
$D\left(\frac{2x+4}{2}\right)=$
$f\left(x\right)=2x+4{,}\ f'\left(x\right)=2\ ja\ g\left(x\right)=2{,}\ g'\left(x\right)=0$
$\frac{2\cdot2-0\left(2x+4\right)}{2^2}=\frac{4}{4}=1$