Rachel, Pete, and Brian perform Part 2 of the investigation in this lesson. Rachel walks while Pete and Brian hold the motion sensors. They create the unusual graph at right. The horizontal axis has a mark every 1 s, and the vertical axis has a mark every 1 m.

a. The lower curve is made from the data collected by Pete's motion sensor.
Where was Brian standing and when did he start his motion sensor to create the upper curve?
b. If Pete's curve is the graph of y = f (x), what equation represents Brian's curve?