Question

The graph of a line passes through the two points (-2, 1) and (2, 1). What is the equation of the line written in general

Answer 1

Answer:

y-1=0

Step-by-step explanation:

I'm going to write into y=mx+b form first.

m is the slope and b is the y-intercept.

First step is to find the slope.

To find the slope given two points you can use m=(y2-y1)/(x2-x1).

Instead, I like to line up the points and subtract vertically.  Then put 2nd difference on top of 1st difference.

Let's do that:

 (-2,1)

- (2,1)

--------

 -4, 0

The slope is 0/-4=0.  That means the line is horizontal and is of the form y=a number.

If you look at the points, you see the y-coordinate doesn't change.  The y-coordinate is always 1.  So the equation for the line is y=1.

If we subtract 1 on both sides we get y-1=0.

So general form is Ax+By+C=0 which is why I decide to move the one on the other side of the equation.  

If I had noticed earlier that the y-coordinates were the same I would have stopped and say y=whatever y-coordinate I seen. However, I really didn't take notice of that until after I found the slope.