Question

Write an equation in slope-intercept form of the line through points S(–1, –4) and T(3, 4)

Answer 1

Ok this is easy to do. You need two things to make an equation: a point and the slope.

Answer 2

We have two points, so we can only either one.

Now for the slope, we need to use the formula for finding slope. Do you remember the formula

Answer 3

okay

Answer 4

Ok so we plug in the points. Let S be (x2,y2) and let T be (x1, y1)

Answer 5

we can also let S be (x1, y1) and T be (x2,y2). It doesn't matter

Answer 6

I'll let S be (x1, y1) and T be (x2, y2). Ok so all we have to do is plug in these numbers into the formula and see what the slope is.

Answer 7

Plug them in, then solve the slope and tell me what you get.

Answer 8

okay

Answer 9

Plug in -1 for x1, -4 for y1, 3 for x2, and 4 for y2.

Answer 10

4+4
----
3+1 right?

Answer 11

Yup, and that simplifies to 2.

Answer 12

We now have our slope, and at least one point on the line. We have all we need to find the equation.

Answer 13

okay

Answer 14

Do you remember the point-slope formula?

Answer 15

y-y1=m(x-x1)

Answer 16

Yup so just plug in 2 for m.

Answer 17

ok

Answer 18

For x1 and y1, you can use EITHER (3,4) or (-1,-4).

Tip:
Don't take the x-value of one and the y-value of the another.
For example don't do (3,-4).

Answer 19

So let's try it with (3,4).
Our x1 is 3 in this case and our y1 is 4.

Answer 20

okay

Answer 21

Try plugging these into y-y1= m(x-x1) and see what you get.

Answer 22

(y-3)=2(x-4)

Answer 23

Great, so all we have to do now is put the equation into slope-intercept form

Answer 24

Do you know how to do that?

Answer 25

okay

Answer 26

no Thats what im struggling with the most

Answer 27

Ok so first of all. Do you see the part

2(x-4)

Answer 28

yes

Answer 29

We use the distributive property. Do you know how to do it?

Answer 30

yes

Answer 31

2x-4

Answer 32

Well that's almost correct

Answer 33

is it y=2x-2 ?

Answer 34

Yup the answer is y = 2x-2

Answer 35

But when you do the distributive rule, you shouldn't get 2x-4

Answer 36

You should learn this as this will come up in math for your entire high school