## Geometry: Common Core (15th Edition)

To determine if two lines are perpendicular, parallel, or neither, we need to look at their slopes. Perpendicular lines have slopes that are negative reciprocals of one another. Parallel lines have the same slope. The lines given are in slope-intercept form, which is given by the formula: $y = mx + b$, where $m$ is the slope of the line, and $b$ is its y-intercept. In the equation $y = -2x$, the slope is $-2$. In the equation $y = -2x + 4$, the slope is also $-2$. Since the slopes are the same, these lines are parallel.