### Home > GB8I > Chapter 7 Unit 8 > Lesson INT1: 7.2.2 > Problem7-104

7-104.

Without graphing, determine which of the following equations represents lines that are parallel to each other. Which are perpendicular? Show how you know.

1. $–3x + y = 5$

1. $–5x + y = 3$

1. $x + 5y = -15$

1. $-15x + 5y = -25$

Put each equation into slope-intercept form
($y = mx + b$, where $m$ is the slope and $b$ is the $y$-intercept). That means to solve for $y$.

Compare the slopes.
If they are equal then they are parallel.
If they are the negative reciprocal of each other then they are perpendicular.