Step 1. We will put the equation of the line in slope-intercept form given as y=mx+b where m is the slope and b is the y-intercept when x=0 or at point (0,b).
Step 2. The slope of the line m is given as
where for our example is x1=-8, y1=-12, x2=9 and y2=-12 (think of ). You can choose the points the other way around but be consistent with the x and y coordinates. You will get the same result.
Step 3. Substituting the above values in the slope equation gives
Step 4. The slope is calculated as or
Step 5. Now use the slope equation of Step 2 and choose one of the given points. I'll choose point (9,-12). Letting y=y2 and x=x2 and substituting in the slope equation given as,
Step 6. Multiply both sides of equation by x-9 to get rid of denominator found on the right side of the equation
This equation defines a horizontal line. There is no X intercept. Y intercept is
I hope the above steps were helpful.
For FREE Step-By-Step videos in Introduction to Algebra, please visit http://www.FreedomUniversity.TV/courses/IntroAlgebra and for Trigonometry visit http://www.FreedomUniversity.TV/courses/Trigonometry.