Manipulate Function and Regression Formulas

[mrashy1]

I'm trying to learn R on the swirl package "Least Squares Estimation" and am having two problems.

1. It mentioned using the manipulate function but when I've tried to use it, it says that it can't find the function.
2. In this lesson, I've had to plot regression lines and there are parts where it wants me to view the formulas for the slope of the regression line.
   However, I a having difficulty doing this. I believe it said earlier that I can access it by clicking on the gear function on the upper left of graph but it is not appearing.
   Thanks