Help? Please and thank you! What is the y coordinate of the y−intercept of the line that passes through the points
(−3, −1) and (1, 7)?

- anonymous

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- anonymous

-3 -1
1 7|dw:1377494318035:dw|

- anonymous

You have to find the slope of the line!

- anonymous

Slope is...\[\frac{ RISE }{ RUN }\]

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## More answers

- anonymous

Lagging is my life.

- anonymous

would that be equal to 1/2 for slope? or no?

- anonymous

Right:)

- anonymous

Well, what is my question asking for? the y coordinate?

- anonymous

Little confused.-.

- anonymous

Yes! To find where the line crosses the Y axes!

- anonymous

-2, 0? Random guess. Lol

- anonymous

\[y – y _{1} = m(x – x _{1})\]

- anonymous

Now using that formula I gave you plug in one of the Points that are given and solve for y.

- anonymous

-1 + 7 = m(-3 + 1)

- anonymous

- 7*

- anonymous

Not exactly...Only use one set of points and plug it into the y and x with a tiny 1...

- anonymous

More like...
y+1= M(x+3)

- anonymous

And M means slope so plug that in too!

- anonymous

y + 1 = 1/2(x + 3)

- anonymous

Yup, now solve for Y.

- anonymous

y = 1/2x + 1/2 ?

- anonymous

Yes:)

- anonymous

This form is call slope intercept form. To find y plug in 0 for X.

- anonymous

y = 1/2(0) + 1/2 y = 1/2 ?

- anonymous

(0,1/2)

- anonymous

Now, this will be tricky to put in the written response, because fractions turn from 1/2 to 12. Lol. Should I just put 0.5?

- anonymous

Wait...before you write it lets check it...cause something doesnt seem right...

- anonymous

I feel like it should be a whole number, my teacher said it should be for these ones.

- anonymous

I think is should be (0,5)...

- anonymous

@mathstudent55 Maybe they know if we did anything wrong.

- anonymous

I figured out!

- anonymous

@Luigi0210

- anonymous

The slope is 2!

- anonymous

we have to redo that with the slope of 2.

- anonymous

Because its Y/X not X/Y.

- anonymous

OpenStudy is lagging for me.

- anonymous

Its okay! it is (0,5)

- anonymous

\[y+1=2(x+3)\]

- anonymous

\[y=2x+5\]

- anonymous

@Luigi0210 I really need to know if he's right. I'm so confused.

- anonymous

Sorry for confusing you...:(

- anonymous

http://www.webmath.com/_answer.php
Its right, check...

- anonymous

Only if OpenStudy was a real person...

- Luigi0210

So you're just looking for the y-coordinate of the y intercept?

- anonymous

Yes.

- Luigi0210

Well you know that the y-intercept is when x=0 right?

- anonymous

Yes, but now I don't even know what the slope is anymore. 1/2 or 2 or 5 lol.

- Luigi0210

Slope is:
\[m=\frac{y2-y1}{x2-x1}\]

- anonymous

-3, -1 1, 7

- anonymous

-1 - 7
------
-3 - 1 ?

- Luigi0210

Just plug them in and solve.
and either way works, you get the same answer

- anonymous

-8
--
-4 ?

- Luigi0210

Yup, making the slope 2.
Now we plug that information into the point-slope formula:
y-y1=m(x-x1)

- Luigi0210

Open was right so far, except for the slope

- anonymous

y - 1 = 2(x - 7) ?

- Luigi0210

Yea, not just distribute.

- Luigi0210

*now

- anonymous

y = 2x - 13?

- Luigi0210

Yup!

- anonymous

Now what?

- Luigi0210

Now we find the y-intercept
Meaning that we plug in where ever there is an x. This will give us the y value we are looking for.

- Luigi0210

*0

- anonymous

What do we use for x? What number?

- anonymous

0 = 2x - 3?

- anonymous

-13......let me type please OpenStudy please...

- Luigi0210

Ah, plug 0 in for x, not y

- anonymous

y = 2(0) - 13 y = -13?

- Luigi0210

Yup, and that's it Mikeyy :)

- anonymous

I feel like that would be one weird y-intercept from where the two dots are on a graph..

- Luigi0210

Your ordered pair is (-13, 0)

- Luigi0210

*(0, -13)

- anonymous

Alright thanks :P

- Luigi0210

Mikeyy..

- anonymous

Yes?

- anonymous

Lol. Answer wasn't -13 but I still got a 88. and I have a chance to get a 90 with my written response...

- Luigi0210

Yes I was about to say that.. sorry buddy :(
I just realized that we used the wrong points for the point-slope formula.

- Luigi0210

The answer was actually (0, 5) and the equation was y=2x+5

- anonymous

It's fine. I had to get over a 60 and I did. So, I'm happy. I need to get off OP before it screws me another time. thanks again

- Luigi0210

Alright, and you're welcome :)

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