http://www.ck12.org Chapter 3. Parallel and Perpendicular Lines
Solution: Graph the two lines and determine the perpendicular slope, which is−^12. Find a point ony= 2 x+4,
let’s say (-1, 2). From here, use the slope of the perpendicular line to find the corresponding point ony= 2 x−1. If
you move down 1 from 2 and over to the right 2 from -1, you will hity= 2 x−1 at (1, 1). Use these two points to
determine the distance between the two lines.
d=√
( 1 + 1 )^2 +( 1 − 2 )^2
=
√
22 +(− 1 )^2
=
√
4 + 1
=
√
5 ≈ 2. 24 unitsThe lines are about 2.24 units apart.
Notice that you could have used any two points, as long as they are on the same perpendicular line. For example,
you could have also used (-3, -2) and (-1, -3) and you still would have gotten the same answer.