Here's a simple voltage divider. I'm learning Thevenin Circuits now and we use the formula for Thevenin Voltage a lot (very useful!) but I'm not sure how the formula arises. My professor said I can derive it using Kirchoff's laws by first finding $I_{load}$ in terms of $V, R_1, R_2$ and $R_{load}$ but I'm lost. Any help would be appreciated.