Aloha :)
\( k_{a}(t)=\underbrace{296 \cdot e^{2,55}}_{=\text{const}}+50,32\underbrace{(t-15)}_{=u} \cdot \underbrace{e^{2,55-a \cdot(t-15)}}_{=v} \)
\( k'_{a}(t)=50,32\cdot\underbrace{1}_{=u'} \cdot \underbrace{e^{2,55-a \cdot(t-15)}}_{=v} + 50,32\underbrace{(t-15)}_{=u} \cdot \underbrace{\overbrace{e^{2,55-a \cdot(t-15)}}^{\text{äußere}}\cdot\overbrace{(-a)}^{\text{innere}}}_{=v'} \)
\( k'_{a}(t)=50,32\cdot e^{2,55-a \cdot(t-15)}-50,32\,a(t-15)\cdot e^{2,55-a \cdot(t-15)}\)
\( k'_{a}(t)=50,32\cdot e^{2,55-a \cdot(t-15)}\left(1-a(t-15)\right)\)