TeX source:
\begin{array}{rclcl} \mathbb{D} &=& \mathbb{R} \cr\cr 4 \cdot e^{25x+18}-1 &=& 51 &\vert& +1 \cr 4 \cdot e^{25x+18} &=& 52 &\vert& :4 \cr e^{25x+18} &=& 13 &\vert& \ln() \cr \ln(e^{25x+18}) &=& \ln(13) \cr 25x+18 &=& \ln(13) &\vert& -18 \cr 25x &=& \ln(13)-18 &\vert& :25 \cr x &=& \dfrac{\ln(13)-18}{25} \approx -0{,}62 \cr\cr \mathbb{L}&=&\left\{\dfrac{\ln(13)-18}{25}\right\} \end{array}