Question 396931: I'm working on the Linear Equations in my Alegbra book. I have a graph with a horizontal X line and a vertical Y line. There is a line that slopes down from left to right. My problem is asking me to find the slope, the y-intercept, and write the equation.
The line intercepts the Y line at 1, then the X line at 2. I figured the slope is -1/2 since {delta y = -2} & {delta x = 4}. I believe the y-intercept is just 2, but I'm totally questioning myself on this & have no idea how to write the equation. Can you help me please?
Answer by solver91311(24713)   (Show Source):
You can put this solution on YOUR website!
Let's start by using the correct words to describe things. Not the X-line or Y-line, it is the x-axis and the y-axis.
If the line crosses the y-axis at 1, then the coordinates of that point are (0,1). If the line crosses the x-axis at 2, then the coordinates of that point are (2,0).
The slope of your line is indeed  . Use the slope formula:
where ) and ) are the coordinates of two points on your line. We determined the coordinates of two points by using the intercept values, so:
I'm not sure where you got the idea that  and  unless there is another point or two defined on your line that you didn't tell us about. Using the coordinate differences on the two intercepts (reading left to right),  and 
Once you have the slope and the y-coordinate value of the y-intercept, writing an equation that represents the line is easy. You have the information to write your equation in slope-intercept form, namely
where  is the slope number and  is the y-coordinate of the y-intercept. For your problem, that is  and  , hence:
From there you can use a little algebra to put the equation into Standard form, namely:
For you:
John
My calculator said it, I believe it, that settles it
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