Question

Could someone please help me get this one started?

Find an equation of the line that passes through the points (1,4) and (-7,-4)

Answer 1

1. Insert each point into y = mx + b, creating two equations.

Answer 2

How do I figure which number to plug in where in the equation?

Answer 3

Because
(x,y) = (1,4)
(x,y) = (-7,-4)

Answer 4

So

4 = 1m + b
-4 = -7m + b

Answer 5

2. Isolate b in both equations

Answer 6

ok, let me try this...lol

Answer 7

ok. I'm drawing a blank... been a long day

Answer 8

Did you isolate b in both equations yet?

Answer 9

I'm having a brain fart as to how that is done and cannot find it in my textbook.

Answer 10

http://www.purplemath.com/modules/strtlneq2.htm

Answer 11

Isolate b in both equations:
Subtract 1m from both sides:
4 - 1m = b

Add 7m to both sides:
-4 + 7m = b

Answer 12

3. Set expressions b = b, then solve for m

Answer 13

y=x+3?

Answer 14

crap

Answer 15

What steps did you use to figure that out?

Answer 16

after you reminded me how to isolate B, +3 was the outcome for both, so I plugged in the rest of the information and failed horribly from there.

Answer 17

So you set b = b to get

4 - 1m = -4 + 7m

then solved for m, correct?

Answer 18

not at all like that...

Answer 19

Well that is what you are supposed to do. I can't imagine you doing anything other than that.

Answer 20

I'm just the bad at math. lol, but I'm trying it again

Answer 21

ok, the only thing that I am seeing here is to simplify down to 5m and 3m, but I know that neither of those will get me anywhere near the equation that I need.

Answer 22

So from there, I'm assuming that you added 4 to both sides, then added 1m to both sides to get
4 + 4 = 1m + 7m

Answer 23

right?

Answer 24

I would lie if I said yes

Answer 25

Well, that's what you do. Can you solve for m from there?

Answer 26

hang on, I'll show you how I did it

Answer 27

Why would I want to see how you did it the wrong way?

Answer 28

4-1m=-4+7m
-4 +4
-1m+7m
6m

then somehow on my work I had 5m+3m=8m

Answer 29

I am awful at this stuff

Answer 30

You don't add 4 on one side then subtract 4 on the other.

Answer 31

What ever operation you choose to perform, you do that to BOTH sides.

Answer 32

ok, so I don't clear to the left of the = in each one and then combine the numbers next to m?

Answer 33

No, you use inverse operations so that you have like terms on each side.

Answer 34

So you should have ended up with 4 + 4 on one side and 1m + 7m on the other side.

Answer 35

so that gives me 8=8m^2

Answer 36

You mean 8 = 8m

You would only get m^2 if you multiplied , which you did not.

Answer 37

If you see a plus sign between two expressions, you add, not multiply.

Answer 38

That's right, forgot that rule.

Answer 39

You forgot how to add?

Answer 40

lol no, the rule of only getting m^2 if multiplication were used.

Answer 41

Did you solve for m yet?

Answer 42

not yet

Answer 43

I can't imagine what is taking you so long.

Answer 44

y=7x+7

Answer 45

Okay, now you're just going off on a tangent

Answer 46

This is what happens when you try to walk someone through a problem.

Answer 47

Now, I'm just going to post the solution.

Answer 48

1. Insert (1,4) and (-7,-4) into y = mx + b, creating two equations:
4 = 1m + b
-4 = -7m + b

2. Isolate b in both equations to get:
4 - 1m = b
-4 + 7m = b

3. Set expressions b = b to get:
4 - 1m = -4 + 7m

4. Add 4 to both sides, then add 1m to both sides:
4 + 4 = 1m + 7m

5. Combine like terms to get:
8 = 8m

6. Divide both sides by 8 to isolate and solve for m:
8/8 = m
1 = m

7. Insert the value of m into one of the equations in step 2:
4 - 1m = b
4 - 1(1) = b
4 - 1 = b
3 = b

8. The equation of the line is y = x + 3

Answer 49

You got y = x + 3 the first time, but you couldn't show how you got it.

Answer 50

I said that I was awful at this subject. I tried my best, and I am sorry if you lost patience with me. There is no need to be crass or insulting.

Answer 51

I wasn't trying to be. I was just saying that I asked you to post your steps for how you got y = x + 3 the first time.