pau08
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
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ChrisV
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first find the slope, m=(y2-y1)/(x2-x1)
ChrisV
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then write it in slope intercept form
y-y1=m(x-x1)
Directrix
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What if I make up two points and work the problem I made up? Will that help?
pau08
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okey....
Directrix
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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
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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
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One of our points will be (x1, y1) and the other (x2, y2) It does not matter which is which.
Directrix
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Let (x1,y1) be (2, -1) and let (x2, y2) be (-4, -5)
Questions so far?
pau08
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what is y=mx+b
Directrix
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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.
pau08
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ah okey
Directrix
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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
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Focus on cranking out this slope right now.
pau08
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okey
Directrix
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|dw:1329213587734:dw|
Directrix
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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
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Do you follow how the slope came to be 2/3?
pau08
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ah okey
pau08
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yes
pau08
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you simplify it
pau08
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|dw:1329268007717:dw|
Directrix
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Yes.
Directrix
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Hey, I like "okey." I understand it means "yes."
Directrix
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Okey, now we use the point slope formula to get the equation of the line.
Directrix
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y - y1 = m (x - x1)
y - y1 = (2/3) ( x - x1)
pau08
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okey
can i solve it?
Directrix
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(x1,y1) be (2, -1) from above.
y - (-1) = (2/3) ( x - 2)
pau08
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oh, i change my mind
i don't want to answer it
Directrix
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We're almost finished. I'll finish if you have to go.
pau08
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i'll have to go now eh...
can we finish it now??
Directrix
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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
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3y +3 = 2 (x-2)
3y + 3 = 2x - 4
pau08
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transpose it, right?
Directrix
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Yes, thought you left, :)
3y = 2x - 7
pau08
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so the answer id -2x+3y=-4-3
pau08
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the final answer is 2x-3y=7
Directrix
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y = (2/3) x - 7/3 in y = mx + b form where m is the slope and (-7/3) is the y-intercept.
Directrix
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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
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Just takes practice like anything else. :)
pau08
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haha....thanks for your help.......what is the answer?
Directrix
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y = (2/3) x - 7/3
pau08
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ah...........T.Y.P
Directrix
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Glad to help.