Chapter 5: Section 5.7, page 75

In the grey box at the top of the page, there is an error in the multiplication operations. They should read:

-5 * -1 =  5
 5 * -1 = -5
 1 * -1 = -1
-1 * -1 =  1

The point here is that we are demonstrating how multiplying by -1 reverses the polarity of a number.