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Homework Help: Quick question. Point-Slope. Thanks!

  1. Sep 17, 2010 #1
    **Quick question. Point-Slope. Thanks!

    1. The problem statement, all variables and given/known data

    Ok i get all of it, except that last part. Here ill show you. Point-Slope question.

    (4, -3), m = -2


    y + 3 = -2(x - 4) which then becomes y+3 = -2x + 8)


    subtract 3 from y + 3, and then do it on other side

    which then gives you:

    y = -2x + 5

    Now, I dont get this final part. It says that you go y + 2x, and then -2x + 2x

    which gives you: 2x + y = 5

    I dont get why and how you do that last part? Can anyone please explain?

    2. Relevant equations

    3. The attempt at a solution
  2. jcsd
  3. Sep 17, 2010 #2


    Staff: Mentor

    Re: **Quick question. Point-Slope. Thanks!

    Take a look at what eumyang wrote about the properties of equations in post 6 of this thread.

    Rather than repeat what he wrote, it would be better if you took a closer look at that.
  4. Sep 18, 2010 #3


    User Avatar
    Homework Helper

    Re: **Quick question. Point-Slope. Thanks!

    Also, you have to be mindful of which form the answer needs to be in. You didn't specify this in your problem, but I'm guessing that it was supposed to be in standard form, because you say at the end
    [tex]2x + y = 5[/tex]
    which is the standard form of the equation of a line (Ax + By = C). That would be the reason why one would add 2x to both sides in the last step.

    If instead you stopped at
    [tex]y = -2x + 5[/tex],
    then you would have the answer in the wrong form (the above is slope-intercept form). If I were grading this I would have given partial credit because you didn't follow directions.

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