Use the Slope and -Intercept sliders to graph the line . Click and drag the red point to .
Select Perpendicular and check the Show 2nd Line box to graph a line through . Find
the -intercept of line L .
Use the interactive figure to find your answer. Use the left and right arrow keys to move along a slider as
needed.
Click here to launch the interactive figure.
The x-intercept of line L is
. (Type an ordered pair.)

To graph the line , you’ll see a steep line going downwards with a negative slope. The slope of -4 means for every unit you move right, you move down 4 units, making it quite steep! Now, when you drag the red point to the coordinates , this point sits above the line since the y-value is greater than what the line would predict at that x-value.

Next, to find the x-intercept of line L, which is perpendicular to our original line and passes through the point , remember that perpendicular lines have slopes that are negative reciprocals of each other. So, if the slope of our original line is -4, the slope of line L will be . Using point-slope form from point , we can find the equation of line L. Solving for the x-intercept, you’ll discover it crosses the x-axis at the ordered pair .