12: Graph Theory
( \newcommand{\kernel}{\mathrm{null}\,}\)
Thumbnail: A pictorial representation of a simple linear program with two variables and six inequalities. The set of feasible solutions is depicted in yellow and forms a polygon, a 2-dimensional polytope. The linear cost function is represented by the red line and the arrow: The red line is a level set of the cost function, and the arrow indicates the direction in which we are optimizing. (CC0; Ylloh via Wikipedia)