Which of the following is the equation of a line that passes though the points (2,5) and (4,3)

The slope of a line is a measure of how fast the line "goes up" or "goes down". A large slope means the line goes up or down really fast (a very steep line). Small slopes means the line isn't very steep. A slope of zero means the line has no steepness at all; it is perfectly horizontal.

For lines like these, the slope is always defined as "the change in y over the change in x" or, in equation form:

So what we need now are the two points you gave that the line passes through. Let's call the first point you gave, (2,5), point #1, so the x and y numbers given will be called x1 and y1. Or, x1=2 and y1=5.

Also, let's call the second point you gave, (4,3), point #2, so the x and y numbers here will be called x2 and y2. Or, x2=4 and y2=3.

Now, just plug the numbers into the formula for m above, like this:

m=

3 - 5

4 - 2

or...

m=

-2

2

or...

m=-1

So, we have the first piece to finding the equation of this line, and we can fill it into y=mx+b like this:

y=-1x+b

Now, what about b, the y-intercept?

To find b, think about what your (x,y) points mean:

(2,5). When x of the line is 2, y of the line must be 5.

(4,3). When x of the line is 4, y of the line must be 3.

Because you said the line passes through each one of these two points, right?

Now, look at our line's equation so far: y=-1x+b. b is what we want, the -1 is already set and x and y are just two "free variables" sitting there. We can plug anything we want in for x and y here, but we want the equation for the line that specfically passes through the two points (2,5) and (4,3).

So, why not plug in for x and y from one of our (x,y) points that we know the line passes through? This will allow us to solve for b for the particular line that passes through the two points you gave!.

You can use either (x,y) point you want..the answer will be the same:

(2,5). y=mx+b or 5=-1 × 2+b, or solving for b: b=5-(-1)(2). b=7.

(4,3). y=mx+b or 3=-1 × 4+b, or solving for b: b=3-(-1)(4). b=7.

See! In both cases we got the same value for b. And this completes our problem.

The equation of the line that passes through the points

(2,5) and (4,3)

is

y=-1x+7