please answer this:
How will you determine the equation of the line if the given are two points of the line?
i really need the answer...
thank you

- anonymous

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- anonymous

first find the slope, m=(y2-y1)/(x2-x1)

- anonymous

then write it in slope intercept form
y-y1=m(x-x1)

- Directrix

What if I make up two points and work the problem I made up? Will that help?

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## More answers

- anonymous

okey....

- Directrix

Points ( 2, -1 ) and ( -4, -5 ) lie on a line. Find the equation of the line that contains then. Leave your answer in y = mx + b form.

- Directrix

First, get the slope. Think of slope as change in y over change in x.
m designates the slope of a line and has formula [y2 - y1] / x2 - x 1 ] . The y2 is not y^2 but what we call y sub 2 because the 2 is a subscript which is hard to type.

- Directrix

One of our points will be (x1, y1) and the other (x2, y2) It does not matter which is which.

- Directrix

Let (x1,y1) be (2, -1) and let (x2, y2) be (-4, -5)
Questions so far?

- anonymous

what is y=mx+b

- Directrix

That is the form we will leave the equation of our line in. So, if we get something like 2x + 7y = 2/3, then that's not y = mx+b form.

- anonymous

ah okey

- Directrix

You don't have to leave the equation in that form unless instructed to do so. Most books do request that or standard form.

- Directrix

Focus on cranking out this slope right now.

- anonymous

okey

- Directrix

|dw:1329213587734:dw|

- Directrix

4/6 = 2/3 so the slope m is 2/3. Note the use of grouping symbols to help prevent sign problems or "sinus" problems as I call them. :)

- Directrix

Do you follow how the slope came to be 2/3?

- anonymous

ah okey

- anonymous

yes

- anonymous

you simplify it

- anonymous

|dw:1329268007717:dw|

- Directrix

Yes.

- Directrix

Hey, I like "okey." I understand it means "yes."

- Directrix

Okey, now we use the point slope formula to get the equation of the line.

- Directrix

y - y1 = m (x - x1)
y - y1 = (2/3) ( x - x1)

- anonymous

okey
can i solve it?

- Directrix

(x1,y1) be (2, -1) from above.
y - (-1) = (2/3) ( x - 2)

- anonymous

oh, i change my mind
i don't want to answer it

- Directrix

We're almost finished. I'll finish if you have to go.

- anonymous

i'll have to go now eh...
can we finish it now??

- Directrix

y - (-1) = (2/3) ( x - 2)
y + 1 = 2/3 (x - 2)
multiply both sides by 3
3(y + 1) = (3) (2/3) (x-2)

- Directrix

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

- anonymous

transpose it, right?

- Directrix

Yes, thought you left, :)
3y = 2x - 7

- anonymous

so the answer id -2x+3y=-4-3

- anonymous

the final answer is 2x-3y=7

- Directrix

y = (2/3) x - 7/3 in y = mx + b form where m is the slope and (-7/3) is the y-intercept.

- Directrix

Look at the cool graph:
http://www.wolframalpha.com/input/?i=line+%282%2C-1%29+and+%28-4%2C-5%29+

- Directrix

One last word. There is no quick and short way to learn math but once you do learn it, you will be proud of yourself.

- Directrix

Just takes practice like anything else. :)

- anonymous

haha....thanks for your help.......what is the answer?

- Directrix

y = (2/3) x - 7/3

- anonymous

ah...........T.Y.P

- Directrix

Glad to help.

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