Parallel and Perpendicular Lines

Front

What are parallel lines?

Back

Lines in a plane that never meet and have the same slope.

Front

What are perpendicular lines?

Back

Lines that intersect at a right angle (90 degrees).

Front

If two lines have slopes m1 and m2, what condition must be met for them to be perpendicular?

Back

m1 * m2 = -1 (the slopes are opposite reciprocals).

Front

What is the slope of a line perpendicular to a line with slope 3?

Back

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

Front

What is the slope of a line parallel to a line with slope -2?

Back

-2 (the same slope).

Front

How do you find the slope of a line given two points (x1, y1) and (x2, y2)?

Back

Slope (m) = (y2 - y1) / (x2 - x1).

Front

What is the equation of a line in slope-intercept form?

Back

y = mx + b, where m is the slope and b is the y-intercept.

Front

If a line has a slope of 0, what type of line is it?

Back

A horizontal line.

Front

If a line has an undefined slope, what type of line is it?

Back

A vertical line.

Front

What are opposite reciprocals?

Back

Two numbers whose product is -1; for example, 2 and -1/2.