Write the equation of a line that passes through (-2, 0) and (3, 10).

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, (-2,0), point #1, so the x and y numbers given will be called x1 and y1. Or, x1=-2 and y1=0.

Also, let's call the second point you gave, (3,10), point #2, so the x and y numbers here will be called x2 and y2. Or, x2=3 and y2=10.

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

m=

10 - 0

3 - -2

or...

m=

10

5

or...

m=2

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=2x+b

Now, what about b, the y-intercept?

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

(-2,0). When x of the line is -2, y of the line must be 0.

(3,10). When x of the line is 3, y of the line must be 10.

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

Now, look at our line's equation so far: y=2x+b. b is what we want, the 2 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 (-2,0) and (3,10).

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:

(-2,0). y=mx+b or 0=2 × -2+b, or solving for b: b=0-(2)(-2). b=4.

(3,10). y=mx+b or 10=2 × 3+b, or solving for b: b=10-(2)(3). b=4.

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