Find the Equation of a Line: example 4.68

Find an equation of a line that is perpendicular to $y = −4$ that contains the point $(−4, 2)$ . Write the equation in slope–intercept form.

Work it out on paper first. Then open the solution one step at a time, and stop as soon as you can finish on your own.

Solution
The line $y = −4$ is a horizontal line. Any line perpendicular to it must be vertical, in the form $x = a$ . Since the perpendicular line is vertical and passes through $(−4, 2)$ , every point on it has an x-coordinate of $−4$ . The equation of the perpendicular line is $x = −4$ . You may want to sketch the lines. Do they appear perpendicular?

Your turn

The book's Try It right after this example: same idea, new numbers. Only the answer is given.

Find an equation of a line that is perpendicular to the line $y = 1$ that contains the point $(−5, 1)$ . Write the equation in slope–intercept form.

How did it go?