Chalk is fun to draw with, and some people even get really good at using it to make art on the sidewalk. If you don’t like tediously developing such skills, though, you could go another ...

Plot points with coordinates where \(x\) and \(y\) are equal. Three points are sufficient, but more can be plotted. Draw a line through the plotted points. If \(x\) is positive, \(y\) is negative.