Equations of Parallel and Perpendicular Lines

Front

Slopes of parallel lines are...

Back

the same

Front

Slopes of perpendicular lines are...

Back

negative reciprocals

Front

What is the slope of a line parallel to y = 2x + 3?

Back

2

Front

What is the slope of a line perpendicular to y = -1/3x + 4?

Back

3 (the negative reciprocal of -1/3 is 3)

Front

If two lines have slopes m1 and m2, and m1 = m2, what can we say about the lines?

Back

They are parallel.

Front

If two lines have slopes m1 and m2, and m1 * m2 = -1, what can we say about the lines?

Back

They are perpendicular.

Front

What is the slope of the line represented by the equation 3x + 4y = 12?

Back

-3/4 (rearranging to slope-intercept form gives y = -3/4x + 3)

Front

What is the slope of the line represented by the equation y = 5?

Back

0 (this is a horizontal line)

Front

What is the slope of the line represented by the equation x = 2?

Back

Undefined (this is a vertical line)

Front

If a line has a slope of 1, what is the slope of a line parallel to it?

Back

1 (same slope for parallel lines)