## College Algebra (10th Edition)

$d(D, B) = 2$
$d(D, B)$ represents the distance between the points D and B on a number line. If the coordinates of D and B are $d$ and $b$, respectively, then: $d(D, B) = |d - b|$ Based on the given number line, the coordinates of D and B are $1$ and $-1$, respectively. Use the formula above to obtain: $d(D, B) = |1-(-1)| = |1+1| =|2|=2$ Thus, $d(D, B) = 2$