I'm learning how to derive a formula and I do not quite see how to simplify from step one to step two?
step one: $$S_k=S_0 \cdot e^{\frac{W_k+k}{2} \cdot ln(u)+(k-\frac{W_k+k}{2})ln(d)}$$
step two: $$S_k=S_0 \cdot e^{W_k \cdot \frac{ln(u)-ln(d)}{2}+k \cdot \frac{ln(u)+ln(d)}{2}}$$
I tried to distribute the $ln(u)$ and $ln(d)$ but that did not look like I was getting closer.