Writing Equations of parallel and perpendicular lines

Front

What is the equation of a horizontal line?

Back

y = b, where b is the y-intercept.

Front

What is the equation of a vertical line?

Back

x = a, where a is the x-intercept.

Front

What is the slope of a line?

Back

The slope (m) is the ratio of the rise (change in y) to the run (change in x).

Front

What does a positive slope indicate about a line?

Back

A positive slope indicates that the line rises from left to right.

Front

What does a negative slope indicate about a line?

Back

A negative slope indicates that the line falls from left to right.

Front

What are opposite reciprocals?

Back

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

Front

What is the slope of parallel lines?

Back

The slopes of parallel lines are the same.

Front

What is the slope of perpendicular lines?

Back

The slopes of perpendicular lines are opposite reciprocals.

Front

If a line has a slope of 2, what is the slope of a line perpendicular to it?

Back

The slope of the perpendicular line is -1/2.

Front

How do you find the slope from two points (x1, y1) and (x2, y2)?

Back

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