Results 1 to 5 of 5

Math Help - [SOLVED] Find the equation of a line through two points.

  1. #1
    DAD
    DAD is offline
    Newbie
    Joined
    Feb 2009
    Posts
    2

    [SOLVED] Find the equation of a line through two points.

    Hi
    I need to work out the equation, something like Y=3X, for the line that goes through these two points on a graph: (1,4) and (2,3)
    Minds gone blank!
    Thanks kindly.
    Follow Math Help Forum on Facebook and Google+

  2. #2
    Member
    Joined
    Jan 2009
    Posts
    94
    General solution. Equation of a line passing tru point (a,b) and (c,d):

     \frac{x-a}{a-c}=\frac{y-b}{b-d}<br />

    Solve for y. The order of a,b,c,d is important.

    -O
    Follow Math Help Forum on Facebook and Google+

  3. #3
    DAD
    DAD is offline
    Newbie
    Joined
    Feb 2009
    Posts
    2
    Don't know what I'm doing wrong...
    If a=1, b=4, c=2 and d=3

    Then I get x=y-4 which isn't right.

    "solve for y" is confusing me.
    Follow Math Help Forum on Facebook and Google+

  4. #4
    Member
    Joined
    Jan 2009
    Posts
    94
    a=1, b=4, c=2 and d=3
    <br />
\frac{x-a}{a-c}=\frac{y-b}{b-d} \rightarrow<br />
\frac{x-1}{1-2}=\frac{y-4}{4-3} \rightarrow<br />
\frac{x-1}{-1}=\frac{y-4}{1} \rightarrow<br />
-x+1=y-4<br />
    Gives:
    <br />
y=-x+5<br />

    -O
    Follow Math Help Forum on Facebook and Google+

  5. #5
    MHF Contributor

    Joined
    Apr 2005
    Posts
    15,792
    Thanks
    1532
    Quote Originally Posted by DAD View Post
    Hi
    I need to work out the equation, something like Y=3X, for the line that goes through these two points on a graph: (1,4) and (2,3)
    Minds gone blank!
    Thanks kindly.
    "Something like Y= 3X" would pass through (0,0). It would be better to use the more general y= mx+ b which works for every non-vertical line. Since the line passes through (1, 4), x= 1, y= 4 satisfy the equation: 4= m(1)+ b or m+ b= 4. Since the line passes through (2, 3), x= 2, y= 3 satisfy the equation: 3= m(2)+ b or 2m+ b= 3. You can solve those two equations for m and b and so get the equation.
    Follow Math Help Forum on Facebook and Google+

Similar Math Help Forum Discussions

  1. Replies: 1
    Last Post: March 25th 2011, 02:49 PM
  2. Replies: 0
    Last Post: April 25th 2010, 06:53 PM
  3. [SOLVED] Find equation of a plane through three points
    Posted in the Advanced Algebra Forum
    Replies: 0
    Last Post: March 6th 2010, 05:20 AM
  4. Replies: 2
    Last Post: September 4th 2009, 10:19 PM
  5. Replies: 5
    Last Post: March 11th 2009, 01:14 PM

Search Tags


/mathhelpforum @mathhelpforum