Chapter 4 - Writing Linear Functions - 4.3 - Writing Equations of Parallel and Perpendicular Lines - Exercises - Page 191: 5

Lines $a$ and $c$ have the same slope, so they are parallel.

Slope of line $a$ $=\frac{y_{2}-y_{1}}{x_{2}-x_{1}}=\frac{0-(-2)}{1-(-1)}=\frac{2}{2}=1$ Slope of line $b$ $=\frac{-2-2}{2-4}=\frac{-4}{-2}=2$ Slope of line $c$ $=\frac{1-2}{-1-0}=\frac{-1}{-1}=1$ Lines $a$ and $c$ have the same slope, so they are parallel.